Story highlights U.S. State Department warns Americans against non-essential travel to Ukraine 
 
 "There will be costs for any military intervention in Ukraine," President Barack Obama says 
 
 "We are strong enough to defend ourselves," Ukrainian ambassador says 
 
 Russian President Vladimir Putin to EU leaders: Ukraine must avoid an escalation of violence 
 
 Tension dramatically mounted in Ukraine's Crimea region Friday as its ambassador to the United Nations warned Russia against any further violation of its territorial borders, a warning that came as the United States urged Russia to pull back from the region or face possible consequences. 
 
 "We are now deeply concerned by reports of military movements taken by the Russian Federation inside Ukraine," U.S. President Barack Obama said in televised comments from the White House. 
 
 "...It would be a clear violation of Russia's commitment to respect the independence and sovereignty and borders of Ukraine and of international laws." 
 
 Obama said any violation of Ukraine's sovereignty and territorial integrity would be "deeply destabilizing, and he warned "the United States will stand with the international community in affirming that there will be costs for any military intervention in Ukraine." 
 
 The remarks were the latest in a series of fast-moving developments that saw Ukrainian officials grappling with rising secessionist passions in the Russian-majority region, where the airspace has been closed and communications have been disrupted. 
 
 Photos: Photos: Crisis in Ukraine Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian tanks are transported from their base in Perevalne, Crimea, on Wednesday, March 26. After Russian troops seized most of Ukraine's bases in Crimea, interim Ukrainian President Oleksandr Turchynov ordered the withdrawal of armed forces from the peninsula, citing Russian threats to the lives of military staff and their families. Hide Caption 1 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian marines wave as they leave a base in Feodosia, Crimea, on Tuesday, March 25. Hide Caption 2 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian sailors stand on the deck of the corvette ship Suzdalets in the bay of Sevastopol, Crimea, on March 25. Hide Caption 3 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian militia members remove a local resident as Russian troops assault the Belbek air base, outside Sevastopol, on Saturday, March 22. Following its annexation of Crimea, Russian forces have consolidated their control of the region. Hide Caption 4 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Soldiers in unmarked uniforms sit atop an armored personnel carrier at the gate of the Belbek air base on March 22. Hide Caption 5 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Russian sailor holds the Russian Navy's St. Andrew's flag while standing on the bow of the surrendered Ukrainian submarine Zaporozhye on March 22 in Sevastopol. Hide Caption 6 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian President Vladimir Putin signs the final decree completing the annexation of Crimea on Friday, March 21, as Upper House Speaker Valentina Matviyenko, left, and State Duma Speaker Sergei Naryshkin watch. Hide Caption 7 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian serviceman leaves a Ukrainian military unit that Russian soldiers took control of in Perevalne on March 21. Hide Caption 8 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian border guards run during training at a military camp in Alekseyevka, Ukraine, on March 21. Hide Caption 9 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian soldiers patrol the area surrounding a Ukrainian military unit in Perevalne on Thursday, March 20. Hide Caption 10 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian protesters remove the gate to the Ukrainian navy headquarters as Russian troops stand guard in Sevastopol on Wednesday, March 19. Hide Caption 11 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian forces walk inside the Ukrainian navy headquarters in Sevastopol on March 19. Hide Caption 12 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A member of pro-Russian forces takes down a Ukrainian flag at the Ukrainian navy headquarters in Sevastopol on March 19. Hide Caption 13 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Alexander Vitko, chief of the Russian Black Sea Fleet, leaves the Ukrainian navy headquarters in Sevastopol after pro-Russian forces took it over on March 19. Hide Caption 14 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Russian flag waves as workers install a new sign on a parliament building in Simferopol, Crimea's capital, on March 19. Hide Caption 15 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian military personnel surround a Ukrainian military base in Perevalne on March 19. Hide Caption 16 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Nameplates on the front of the Crimean parliament building get removed Tuesday, March 18, in Simferopol. Hide Caption 17 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – From left, Crimean Prime Minister Sergey Aksyonov; Vladimir Konstantinov, speaker of the Crimean parliament; Russian President Vladimir Putin; and Alexei Chaly, the new de facto mayor of Sevastopol, join hands in Moscow on March 18 after signing a treaty to make Crimea part of Russia. Hide Caption 18 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Demonstrators hold a Crimean flag at Lenin Square in Simferopol on March 18. Hide Caption 19 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian soldiers stand guard at a checkpoint near Strilkove, Ukraine, close to Crimea on Monday, March 17. Hide Caption 20 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Former boxer and Ukrainian politician Vitali Klitschko addresses reporters in Kiev, Ukraine, on March 17. Hide Caption 21 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian troops stand guard in front of the Ukrainian Parliament building in Kiev on March 17. Hide Caption 22 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian man applies for the National Guard at a mobile recruitment center in Kiev on March 17. Hide Caption 23 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Civilians walk past riot police in Simferopol on March 17. Hide Caption 24 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian soldier stands on top of an armored vehicle at a military camp near the village of Michurino, Ukraine, on March 17. Hide Caption 25 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Policemen stand guard outside the regional state administration building in Donetsk, Ukraine, during a rally by pro-Russia activists March 17. Hide Caption 26 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Armed soldiers stand guard outside a Ukrainian military base in Perevalne on March 17. Hide Caption 27 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A man holds a Crimean flag as he stands in front of the Crimean parliament building in Simferopol on March 17. Hide Caption 28 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Crimeans holding Russian flags celebrate in front of the parliament building in Simferopol on Sunday, March 16. Hide Caption 29 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian police officer tries to shield himself from a road block thrown by pro-Russia supporters in Kharkiv, Ukraine, on March 16. Hide Caption 30 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russia demonstrators storm the prosecutor general's office during a rally in Donetsk on March 16. Hide Caption 31 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A child casts her mother's ballot March 16 while holding a Russian flag at a polling station in Simferopol. Hide Caption 32 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A pro-Russian soldier, with the Russian flag behind him, mans a machine gun outside an Ukrainian military base in Perevalne on Saturday, March 15. Hide Caption 33 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A pro-Russian soldier guards the perimeter outside an Ukrainian military base in Perevalne on March 15. Hide Caption 34 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian flags wave in front of a monument dedicated to Soviet Union founder Vladimir Lenin during a pro-Russia rally in Simferopol's Lenin Square on March 15. Hide Caption 35 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Evgenyi Batyukhov cries March 14 at the site where pro-Russian and pro-Ukrainian activists clashed the night before in Donetsk, Ukraine. Hide Caption 36 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A line of policemen stand in front of a bus of pro-Ukrainian activists as pro-Russian supporters confront them during a rally in Donetsk on Thursday, March 13. Hide Caption 37 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian supporters clash with pro-Ukrainian activists in Donetsk on March 13. Hide Caption 38 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Recent Academy Award winner Jared Leto walks through Independence Square in Kiev on March 13. During his Oscars acceptance speech in early March, the actor spoke to protesters in Ukraine and Venezuela saying, "We're thinking of you tonight." Hide Caption 39 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A member of a pro-Russian self-defense unit checks a polling station near Simferopol on March 13. Hide Caption 40 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian soldier looks out of the window of a regional military building with a poster reading "Ukraine's armed forces wait for you!" in Donetsk on March 13. Hide Caption 41 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – An armed Cossack stands guard at a checkpoint on the road from Simferopol to Sevastopol on March 13. Hide Caption 42 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A pro-Russian soldier speaks to a truck driver outside the Ukrainian infantry base in Perevalne on Wednesday, March 12. Hide Caption 43 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Cossacks stand guard at Crimea's regional parliament building in Simferopol on March 12. Hide Caption 44 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Soldiers are seen aboard the Ukrainian ship Slavutych in the harbor of Sevastopol on Tuesday, March 11. Hide Caption 45 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian naval officers board a boat in front of the Russian minesweeper Turbinist in Sevastopol's harbor on March 11. Hide Caption 46 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People shout slogans during a pro-Russia rally in Donetsk on Sunday, March 9. Hide Caption 47 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian police detain a demonstrator during a pro-Russian rally in Donetsk on March 9. Hide Caption 48 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russia protesters remove a Ukrainian flag from a flagpole taken from a government building in Donetsk on March 9. Hide Caption 49 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Cossacks and other pro-Russian forces stand guard outside a government building in Simferopol on Saturday, March 8. Hide Caption 50 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian soldiers load armored personnel carriers into boxcars in the western Ukrainian city of Lviv on March 8. Hide Caption 51 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Armed men believed to be Russian military march in a village outside Simferopol on Friday, March 7. Hide Caption 52 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russia protesters demonstrate outside the Belbek air base, near Sevastopol, on Thursday, March 6. Hide Caption 53 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian navy officer looks at the scuttled, decommissioned Russian vessel Ochakov from the Black Sea shore outside the town of Myrnyi, Ukraine, on March 6. Russian naval personnel scuttled the ship, blockading access for five Ukrainian naval vessels. Hide Caption 54 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A member of the Russian military patrols around Perevalne on March 6. Hide Caption 55 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Servicemen guard a checkpoint at a Ukrainian navy base in Perevalne on March 6. Hide Caption 56 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian troops guard the Belbek air base on March 6. Hide Caption 57 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A woman walks past barricades March 6 that were set up by anti-government protesters in Kiev's Independence Square. Hide Caption 58 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A sailor guards the Ukrainian Navy ship Slavutych in the Bay of Sevastopol on Wednesday, March 5. Hide Caption 59 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People wait in line for food distribution in Independence Square on March 5. Hide Caption 60 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian sailors carry meat to their vessel in the Sevastopol harbor on March 5. Hide Caption 61 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Riot police stand at the entrance of a regional administrative building during a rally in Donetsk on March 5. Hide Caption 62 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian police officer gives instructions to members of the media in front of the business class lounge of the Simferopol airport on March 5. Hide Caption 63 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russia demonstrators wave a Russian flag after storming a regional administrative building in Donetsk on March 5. Hide Caption 64 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Demonstrators break a police barrier as they storm a regional administrative building in Donetsk on March 5. Hide Caption 65 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian military recruits line up to receive instructions in Kiev's Independence Square on Tuesday, March 4. Hide Caption 66 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People stand on the Ukrainian Navy ship Slavutych while it's at harbor in Sevastopol on March 4. Mattresses were placed over the side of the ship to hinder any attempted assault. Hide Caption 67 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian troops watch as a Russian navy ship blocks the entrance of the Ukrainian navy base in Sevastopol on March 4. Hide Caption 68 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A woman photographs pro-Russian soldiers guarding Ukraine's infantry base in Perevalne on March 4. Hide Caption 69 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – U.S. Secretary of State John Kerry, wearing a blue scarf, visits a shrine March 4 for the people who were killed in February during anti-government protests in Kiev. Hide Caption 70 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Yuli Mamchun, the commander of the Ukrainian military garrison at the Belbek air base near Sevastopol, salutes on March 4. Hide Caption 71 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian soldiers stand guard at the Belbek air base on March 4. Hide Caption 72 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian military members march at the Belbek air base on March 4. Hide Caption 73 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian soldiers fire warning shots to keep back Ukrainian military members at the Belbek air base on March 4. Hide Caption 74 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Ukrainian airman puts the Ukrainian national flag over the gate of the Belbek air base as they guard what's left under their control on March 4. Hide Caption 75 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian soldiers aim a grenade launcher and machine gun as they guard positions at the Belbek air base on March 4. Hide Caption 76 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian seamen stand guard on the Ukrainian navy ship Slavutych in the Sevastopol harbor on Monday, March 3. Hide Caption 77 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Oleg, a Ukrainian soldier, kisses his girlfriend, Svetlana, through the gates of the Belbek base entrance on March 3. Tensions are high at the base, where Ukrainian soldiers were standing guard inside the building while alleged Russian gunmen were standing guard outside the gates. Hide Caption 78 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Wives of Ukrainian soldiers walk past Russian soldiers to visit their husbands guarding a military base in Perevalne on March 3. Hide Caption 79 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A Russian soldier guards an area outside Ukraine's military base in the village of Perevalne on March 3. Hide Caption 80 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A sailor looks out a window near the entrance to the Ukrainian navy headquarters in Sevastopol on March 3. Hide Caption 81 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Armed men in military uniform walk outside a Ukrainian military unit near Simferopol on Sunday, March 2. Hundreds of armed men in trucks and armored vehicles surrounded the Ukrainian base Sunday in Crimea, blocking its soldiers from leaving. Hide Caption 82 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Soldiers walk outside a Ukrainian military base in Perevalne as a local resident waves a Russian flag March 2. Hide Caption 83 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Demonstrators shout during a rally in Kiev's Independence Square on March 2. Hide Caption 84 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian soldiers, left, and unidentified gunmen, right, stand at the gate of an infantry base in Perevalne on March 2. Hide Caption 85 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian soldiers guard a gate of an infantry base in Perevalne on March 2. Hide Caption 86 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A woman cries during a rally in Independence Square on March 2. Hide Caption 87 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Protesters hold flags of the United States, Germany and Italy during a rally in Independence Square on March 2. Hide Caption 88 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People attend a morning prayer service at Independence Square on March 2. Hide Caption 89 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A soldier and a truck driver unload bread outside the Ukranian navy headquarters in Sevastopol on March 2. Hide Caption 90 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Heavily armed troops, displaying no identifying insignia and who were mingling with local pro-Russian militants, stand guard outside a local government building in Simferopol on March 2. Hide Caption 91 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A woman waits in front of unidentified men in military fatigues who were blocking a base of the Ukrainian frontier guard unit in Balaklava, Ukraine, on Saturday, March 1. Hide Caption 92 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – U.S. President Barack Obama, in the Oval Office of the White House, talks on the phone March 1 with Russian President Vladimir Putin. Hide Caption 93 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Troops stand guard in Balaklava on March 1. Hide Caption 94 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Heavily armed soldiers displaying no identifying insignia maintain watch in Simferopol on March 1. Hide Caption 95 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People gather around the coffin of a man who was killed during clashes with riot police in Independence Square. Hide Caption 96 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian activists hold Russian flags during a rally in the center of Donetsk on March 1. Hide Caption 97 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian activists clash with Maidan supporters as they storm the regional government building in Kharkiv, Ukraine, on March 1. Hide Caption 98 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A protester stands at a memorial March 1 for the people killed in clashes at Independence Square. Hide Caption 99 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Armed men patrol outside the Simferopol International Airport on Friday, February 28. Hide Caption 100 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – An image provided to CNN by a local resident shows Russian tanks on the move in Sevastopol. Hide Caption 101 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Russian troops block a road February 28 toward the military airport in Sevastopol. The Russian Black Sea Fleet is based at the port city. Hide Caption 102 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Armed men stand guard in front of a building near the Simferopol airport on February 28. Hide Caption 103 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – An armed man wearing no identifying insignia patrols outside Simferopol International Airport on February 28. Hide Caption 104 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Police stand guard outside the Crimea regional parliament building Thursday, February 27, in Simferopol. Armed men seized the regional government administration building and parliament in Crimea. Hide Caption 105 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Police intervene as Russian supporters gather in front of the parliament building in Simferopol on February 27. Hide Caption 106 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A man adds fuel to a fire at a barricade in Independence Square on February 27. Dozens of people were killed during clashes between security forces and protesters. Hide Caption 107 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russia demonstrators wave Russian and Crimean flags in front of a local government building in Simferopol on February 27. Hide Caption 108 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Barricades in front of a government building in Simferopol on February 27 hold a banner that reads: "Crimea Russia." There's a broad divide between those who support the pro-Western developments in Kiev and those who back Russia's continued influence in Crimea and across Ukraine. Hide Caption 109 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Protesters stand in front of a government building in Simferopol on February 27. Tensions have simmered in the Crimea region since the ouster of Ukrainian President Viktor Yanukovych. Hide Caption 110 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Protesters in support of the president's ouster rally in Independence Square, which has been the center of opposition, on Wednesday, February 26. Hide Caption 111 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Security forces stand guard during clashes between opposing sides in front of Crimea's parliament building in Simferopol on February 26. Hide Caption 112 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Pro-Russian demonstrators, right, clash with anti-Russian protesters in front of a government building in Simferopol on February 26. Hide Caption 113 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A police officer gets pulled into a crowd of Crimean Tatars in Simferopol on February 26. The Tatars, an ethnic minority group deported during the Stalin era, rallied in support of Ukraine's interim government. Hide Caption 114 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A man places flowers at a barricade near Independence Square on February 26. Hide Caption 115 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – On February 26 in Kiev, a woman holds a photograph of a protester killed during the height of tensions. Hide Caption 116 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Police guard a government building in Donetsk on February 26. Hide Caption 117 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Protesters remove a fence that surrounds Ukraine's parliament in Kiev on February 26. Hide Caption 118 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People sing the Ukrainian national anthem at Independence Square on Monday, February 24. Hide Caption 119 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Gas masks used by protesters sit next to a barricade in Independence Square on February 24. Hide Caption 120 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A woman cries February 24 near a memorial for the people killed in Kiev. Hide Caption 121 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – People wave a large Ukrainian flag in Independence Square on Sunday, February 23. Hide Caption 122 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Two pro-government supporters are made to pray February 23 in front of a shrine to dead anti-government protesters. Hide Caption 123 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A man and his daughter lay flowers at a memorial for protesters killed in Independence Square. Hide Caption 124 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Former Prime Minister Yulia Tymoshenko speaks at Independence Square on Saturday, February 22, hours after being released from prison. Tymoshenko, considered a hero of a 2004 revolution against Yanukovych, was released after 2½ years behind bars. Hide Caption 125 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Tymoshenko is greeted by supporters shortly after being freed from prison in Kharkiv on February 22. Hide Caption 126 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – A protester guards the entrance to Yanukovych's abandoned residence outside Kiev on February 22. Hide Caption 127 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Anti-government protesters guard the streets next to the presidential offices in Kiev on February 22. Hide Caption 128 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Anti-government protesters drive a military vehicle in Independence Square on February 22. Many protesters said they wouldn't leave the square until Yanukovych resigned. Hide Caption 129 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Ukrainian lawmakers argue during a session of Parliament on Friday, February 21. Hide Caption 130 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Men in Kiev carry a casket containing the body of a protester killed in clashes with police. Hide Caption 131 of 132 Photos: Photos: Crisis in Ukraine Crisis in Ukraine – Protesters cheer after news of an agreement between the opposing sides in Kiev on February 21. Hide Caption 132 of 132 
 
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 Ukraine accused Russian Black Sea forces of trying to seize two airports in Crimea but said Ukrainian security forces prevented them from taking control. 
 
 Ukraine Interior Minister Arsen Avakov earlier characterized the presence at the airport of unidentified armed men, who wore uniforms without insignia, as an "armed invasion." 
 
 The crisis echoed throughout the world, with the U.N. Security Council president holding a private meeting about the crisis enveloping Ukraine and world leaders calling armed groups not to attempt to challenge Ukrainian sovereignty. 
 
 'This group is making a serious mistake' 
 
 At a press conference outside the U.N. Security Council, Ukraine's ambassador to the U.N., Yuriy Sergeyev said the country was prepared to defend itself and urged the U.N.'s moral and political support for the Kiev government, particularly in Crimea. 
 
 Since last week's ouster of President Viktor Yanukovych, Ukraine has faced a deepening schism, with those in the west generally supporting the interim government and its European Union tilt, while many in the east preferring a Ukraine where Russia casts a long shadow. 
 
 Nowhere is that feeling more intense than in Crimea, the last big bastion of opposition to the new political leadership. And Ukraine suspects Russia of fomenting tension in the autonomous region that might escalate into a bid for separation by its Russian majority. 
 
 "We still have a chance to stop the negative developments and separatism," Sergeyev said. 
 
 Sergeyev accused Russia of violating its military agreement by blocking Ukrainian security forces, including its border guards and police, in the region. 
 
 "This group is making a serious mistake challenging our territorial integrity," he said. 
 
 But Russia's ambassador to the United Nations, Vitaliy Churkin, compared the reports of Russian troops taking charge of positions on the ground to rumors that "are always not true." 
 
 "We are acting within the framework of our agreement," he said. 
 
 Even so, U.S. military commanders and intelligence agencies were scrambling Friday to determine what was needed to get a better picture of Russian movements. 
 
 That included an assessment of intelligence gathering, surveillance and reconnaissance needs, a senior U.S. official told CNN. 
 
 The U.S. State Department warned Americans to defer all non-essential travel to Ukraine, particularly the Crimea region, "due to the potential for instability following the departure of former President Yanukovych and the establishment of a new government." 
 
 Meanwhile, Obama is considering not attending the G8 Summit in Sochi, Russia, in June, if Russian troops remain in the Ukraine, a senior administration official familiar with the discussions told CNN. 
 
 Both officials spoke on condition of anonymity. 
 
 Kerry talks to Russian foreign minister 
 
 The Russian Foreign Ministry said maneuvers of armored vehicles from the Russian Black Sea Fleet in Crimea were needed for security and were in line with bilateral agreements. 
 
 U.S. Secretary of State John Kerry said he spoke with Russian Foreign Minister Sergey Lavrov on Friday morning about the airport and military activities, and Lavrov told Kerry that the Russians "are not engaging in any violation of the sovereignty" of Ukraine. Russia has a military base agreement with the country. 
 
 Lavrov told him the military exercises were prescheduled and unrelated to the events in Ukraine, Kerry said. 
 
 "I nevertheless made it clear that that could be misinterpreted at the moment,'' Kerry said, "and there are enough tensions that it is important for everybody to be extremely careful not to inflame the situation and send the wrong messages." 
 
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 Kerry said Lavrov had reaffirmed to him a commitment that Russia would "respect the territorial integrity of Ukraine." 
 
 "We would overwhelmingly stress today that we urge all parties -- all parties; that includes the new interim technical government, rightists, oppositionists and others, anybody in the street who is armed -- we urge all parties to avoid any steps that could be misinterpreted or lead to miscalculation or do anything other than to work to bring that peace and stability and peaceful transition within the governing process within Ukraine," Kerry said. 
 
 Russian response 
 
 In a telephone call with European leaders, Russian President Vladimir Putin stressed the importance of avoiding a further escalation of violence in Ukraine, the Kremlin said in a prepared statement Friday. 
 
 Putin also called for a normalization of the situation, speaking with German Chancellor Angela Merkel, British Prime Minister David Cameron and European Council President Herman Van Rompuy, according to the Kremlin. 
 
 Crimea was handed to Ukraine by the Soviet Union in 1954. Just over half its population is ethnic Russian, while about a quarter are Ukrainians and a little more than 10% are Crimean Tatars, a predominantly Muslim group oppressed under former Soviet leader Josef Stalin. 
 
 Meanwhile, Russian lawmakers introduced two bills Friday to simplify annexing new territories into the Russian Federation and simplify access to Russian citizenship for Ukrainians, the state news agency Itar Tass said. 
 
 One bill also stipulates that the accession of a part of a foreign state to Russia should be taken through a referendum, according to Russian state news agency RIA Novosti. 
 
 Ukraine's President in Russia 
 
 Making his first public appearance since his ouster Saturday, Ukrainian President Viktor Yanukovych said the newly appointed interim government was not legitimate and did not represent the majority of Ukraine's 45 million citizens. 
 
 "I intend to continue the fight for the future of Ukraine against those who, with fear and with terror, are attempting to replace the power," Yanukovych said in Russian, not Ukrainian. 
 
 "Nobody has overthrown me. I was compelled to leave Ukraine due to a direct threat to my life and my nearest and dearest." 
 
 In his hourlong news conference, Yanukovych accused the interim authorities in Ukraine of propagating violence. He spoke against a backdrop of Ukraine's blue-and-yellow flags before reporters in the Russian city of Rostov-on-Don about 700 miles south of Moscow. 
 
 "I never gave any orders to shoot," he said, adding that he sought peace and that the security forces took up arms only when their lives were at risk. 
 
 Yanukovych is wanted in Ukraine on charges connected to the deaths of demonstrators, who were protesting his decision to scrap a European Union trade deal in favor of one with Russia. 
 
 Armed men at airports 
 
 Back in Kiev, Andrii Parubii, chief of national security and defense, said Ukrainian military and police forces had stopped Russian military forces from seizing two airports in the Crimean region. 
 
 The Russian military is on the outside of both airports, Parubii said in a televised news conference from the Ukrainian parliament. 
 
 Weapons were not used during the operation, according to Avakov, the interior minister. 
 
 Russian armored vehicles were moving toward Simferopol, the regional capital, on Friday, the Ukrainian news outlet TSN reported. 
 
 Men in military uniforms had been seen patrolling the airport in Simferopol, as well as a military and civilian airbase in nearby Sevastopol since early Friday. 
 
 Avakov said the armed men at the Sevastopol air base were troops from Russia's Black Sea Fleet, stationed in the port city. They were in camouflage uniforms without military insignia, he said. 
 
 The presence of the armed men has not affected the Simferopol airport, civil aviation authorities said. 
 
 "We are checking to make sure that no radicals come to Crimea from Kiev, from the Ukraine," said one man outside the airport, who didn't give his name. "We don't want radicals, we don't want fascism, we don't want problems." 
 
 Other men outside the airport, dressed in black rather than military fatigues, said they belonged to the pro-Russia Unity Party and had come on the orders of the new Crimean administration -- voted in Thursday after armed men seized regional government buildings. 
 
 Concerned about the latest developments, Ukraine's parliament passed a resolution Friday that demanded Russia halt any activity that can be interpreted as an attack on its sovereignty. 
 
 Moscow alarmed some observers by announcing the surprise military exercises Wednesday in its western and central areas, near the Ukraine border. 
 
 Meanwhile, Ukraine's largest telecom firm was unable to provide data and voice connectivity between Crimea and the rest of Ukraine because unknown people had seized telecommunications nodes and destroyed cables, it said Friday. There is almost no phone connectivity or Internet service across Crimea, said Ukrtelecom, which is the only landline provider. ||||| Media playback is unsupported on your device Media caption Key moments from Viktor Yanukovych's news conference 
 
 Viktor Yanukovych has vowed to fight for Ukraine, in his first public appearance since being ousted as president last week. 
 
 Speaking in Russia, he said he was "not overthrown" but was compelled to leave Ukraine after threats to his life. 
 
 In the latest flare-up, Ukraine accused Russian troops of seizing two airports in Crimea - charges denied by Moscow. 
 
 Russian President Vladimir Putin has called for a rapid return to normality in Ukraine. 
 
 Mr Putin spoke to Western leaders to emphasise "the extreme importance of not allowing a further escalation of violence", the Kremlin said. 
 
 However, Ukraine's foreign ministry has sent a protest note to Moscow citing a violation of airspace and provisions of the treaty regulating the Russian presence in Crimea. 
 
 The note does not give details, but follows unconfirmed reports of Russian planes landing at Simferopol - allegedly with hundreds of Russian troops on board. 
 
 Analysis The picture being presented from Moscow is that events in Crimea are spontaneous - the natural response of local Russian speakers who felt threatened by the new Kiev government. How far the Kremlin is pulling the strings behind the scenes is hard to know. Certainly it is not being admitted openly. But there are signs the Russian government is hardening its stance. The question for President Putin is how far he can push it without risking a full scale confrontation with the West. Maybe he thinks he can have it both ways - encourage more Crimean autonomy but stop short of secession; criticise the new Kiev government but avoid a full break in relations; and try to unnerve Ukraine's young government by heavy-handed manoeuvres on the border without actually invading. But it is a dangerous game. If tensions escalate further, a full scale crisis between East and West may be impossible to avoid. Analysis: Russian shadow boxing 
 
 In other developments: 
 
 Swiss and Austrian authorities block the assets of Viktor Yanukovych and his associates, and launch a corruption probe 
 
 Russian MPs propose new laws that would make it easier for Russia to incorporate parts of Ukraine 
 
 Amid fears of hyperinflation, Ukraine's central bank has put a 15,000 hryvnia (1,000 euro; £820) limit on daily cash withdrawals 
 
 The UN Security Council is set to hold private discussions on the crisis later on Friday 
 
 'Bandit coup' 
 
 "I intend to continue to struggle for the future of Ukraine, against terror and fear," Mr Yanukovych told the news conference in the southern Russian city of Rostov-on-Don. 
 
 "What's going on now is lawlessness, lack of authority, and terror. Decisions in parliament were taken under duress." 
 
 He apologised to the Ukrainian people for not having "enough strength to keep stability" and described his usurpers as "young, neo-fascists". 
 
 He insisted he did not "flee anywhere", explaining that his car was shot at as he left Kiev and he was forced to move around Ukraine amid fears for the safety of himself and his family. 
 
 He said he arrived in Russia "thanks to a patriotically-minded young officer" and was given refuge in Rostov by an old friend. 
 
 Speaking in Russian, Mr Yanukovych said he would return to Ukraine "as soon as there are guarantees for my security and that of my family". 
 
 But he ruled out taking part in elections planned for 25 May, describing them as "illegal". 
 
 Later Ukrainian authorities said they had started moves to have him extradited to Kiev where he is wanted on charges of mass murder. 
 
 Media playback is unsupported on your device Media caption Christian Fraser says barriers and armed men are blocking Sevastopol airport 
 
 And he said the only way out of the crisis is to implement an EU-backed compromise agreement he signed with opposition leaders last week before he was deposed. 
 
 The current turmoil in Crimea was "an absolutely natural reaction to the bandit coup that occurred in Kiev", he said, adding that he was surprised by the restraint shown by Russian President Vladimir Putin so far. 
 
 But he stressed that "military action in this situation is unacceptable" and said he wanted Crimea to remain part of Ukraine. 
 
 'Armed invasion' 
 
 Armed men took over Sevastopol and Simferopol airports in the early hours of Friday. 
 
 Acting national security chief Andriy Parubiy said the airports were back in the control of the Ukrainian authorities, but the men were now manning checkpoints on the surrounding roads. 
 
 Image copyright Reuters Image caption Armed men carrying Russian navy flags arrived at Simferopol airport in several trucks 
 
 Image copyright Getty Images Image caption They have declined to say who they are, and are wearing no identifying insignia 
 
 Image copyright AFP Image caption Men whom Ukraine says are Russian naval troops have also blocked roads to Sevastopol airport 
 
 Image copyright AFP Image caption Meanwhile people are still reeling from the violence in Kiev, which led to the ousting of Mr Yanukovych. 
 
 Witnesses also reported seeing Russian army trucks and helicopters in and around the regional capital Simferopol and Sevastopol, where Russia's Black Sea Fleet is based. 
 
 The move on the airports prompted Ukrainian Interior Minister Arsen Avakov to accuse Russia of carrying out an "armed invasion" of Crimea. 
 
 Crimea's airports Simferopol is the main international terminal, serving the regional capital 
 
 Sevastopol, home to Russia's Black Sea Fleet, has a Soviet-era military airport (Belbek) which was also used for civilian flights until some years ago. Ukrainian air force jets are stationed there 
 
 The Russian Black Sea Fleet has aircraft stationed at other air bases in Crimea (Gvardeyskaya and Kacha) In pictures: Crimea tension 
 
 Russia denied any involvement with the takeover at the airport, but confirmed its armoured vehicles had been on the move around Crimea for "security" reasons. 
 
 On Thursday, a group of unidentified armed men entered Crimea's parliament building by force, and hoisted a Russian flag on the roof. 
 
 They were still in the building when the Crimean parliament later announced it would hold a referendum on expanding the region's autonomy from Ukraine on 25 May. 
 
 Crimea is becoming the lynchpin of a struggle between Ukraine's new leaders and those loyal to Russia, the BBC's diplomatic correspondent Bridget Kendall says. 
 
 The majority of people in Crimea are ethnic Russians, but ethnic Ukrainians loyal to Kiev and Muslim Tatars - whose animosity towards Russia stretches back to Stalin's deportations during World War Two - have formed an alliance to oppose any move back towards Moscow. ||||| SIMFEROPOL, Ukraine (AP) — Russian military were blocking an airport in the Black Sea port of Sevastopol in Crimea near the Russian naval base while unidentified men were patrolling another airport serving the regional capital, Ukraine's new Interior Minister Arsen Avakov said on Friday. 
 
 An unidentified armed man patrols a square in front of the airport in Simferopol, Ukraine, Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings occupied the airport in the... (Associated Press) 
 
 Unidentified armed men guard a building at the airport in Simferopol, Ukraine, on Friday, Feb. 28, 2014. Dozens of armed men in Russian-style military uniforms occupied the airport in the capital of Ukraine's... (Associated Press) 
 
 Unidentified armed men patrol a square in front of the airport in Simferopol, Ukraine, Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings occupied the airport in the capital... (Associated Press) 
 
 An unidentified armed man patrols a square in front of the airport in Simferopol, Ukraine, Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings occupied the airport in the... (Associated Press) 
 
 An unidentified armed man guards a building at the airport in Simferopol, Ukraine, Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings patroled the airport in the capital... (Associated Press) 
 
 An unidentified armed man patrols a square in front of the airport in Simferopol, Ukraine, on Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings occupied the airport in... (Associated Press) 
 
 Unidentified armed men guard a building at the airport in Simferopol, Ukraine, on Friday, Feb. 28, 2014. Dozens of armed men in Russian-style military uniforms occupied the airport in the capital of Ukraine's... (Associated Press) 
 
 An unidentified armed man patrols a square in front of the airport in Simferopol, Ukraine, Friday, Feb. 28, 2014. Dozens of armed men in military uniforms without markings occupied the airport in the... (Associated Press) 
 
 Avakov wrote in a Facebook post that the Belbek international airport in Sevastopol was blocked by military units of the Russian navy. 
 
 "I can only describe this as a military invasion and occupation," Avakov said. 
 
 The Russian foreign ministry refused to comment while a spokesman for the Russian defense ministry was not available for comment. 
 
 Early on Friday, dozens of armed men in military uniforms without markings were seen patrolling the airport in Simferopol, the capital of Crimea. 
 
 An Associated Press photographer saw military men armed with assault rifles Friday morning patrolling the airport. The men, who were wearing uniforms without any insignia, refused to talk to journalists, and it was not immediately clear who they were. 
 
 On Thursday, masked gunmen with rocket-propelled grenades and sniper rifles seized the parliament and government offices in Simferopol and raised the Russian flag over the parliament building. 
 
 The events in the Crimea region have heightened tensions with neighboring Russia. It scrambled fighter jets on Thursday to patrol borders in the first stirrings of a potentially dangerous confrontation reminiscent of Cold War brinksmanship. 
 
 Russia also has granted shelter to Ukraine's fugitive president, Viktor Yanukovych, after recent deadly protests in Kiev swept in a new government. 
 
 Yanukovych has a news conference scheduled Friday in Russia's south near the Ukrainian border. He has not been seen publicly since Saturday, and he declared Thursday in a statement that he remains Ukraine's legitimate president. 
 
 Ukraine's parliament on Thursday elected a new government led by a pro-Western technocrat who promptly pledged to prevent any national break-up. 
 
 Moscow has been sending mixed signals about Ukraine but pledged to respect its territorial integrity. Russian President Vladimir Putin has long dreamed of pulling Ukraine, a country of 46 million people considered the cradle of Russian civilization, closer into Moscow's orbit. 
 
 Ukraine's population is divided in loyalties between Russia and the West. Crimea, which was seized by Russian forces in the 18th century under Catherine the Great, was once the crown jewel in Russian and then Soviet empires. 
 
 It only became part of Ukraine in 1954 when Soviet leader Nikita Khrushchev transferred jurisdiction from Russia, a move that was a mere formality until the 1991 Soviet collapse meant Crimea landed in an independent Ukraine. 
 
 In a bid to shore up Ukraine's fledgling administration, the International Monetary Fund has said it is "ready to respond" to Ukraine's bid for financial assistance. The European Union is also considering emergency loans for a country that is the chief conduit of Russian natural gas to western Europe. 
 
 Ukraine's finance ministry has said it needs $35 billion over the next two years to avoid default. 
 
 __ 
 
 Nataliya Vasilyeva contributed to this report from Moscow. ||||| Photo Advertisement Continue reading the main story 
 
 
 
 
 
 
 
 KIEV, Ukraine — Ukraine’s fragile new government accused Russia of trying to provoke a military conflict by invading the Crimea region on Friday, while in Washington President Obama issued a stern warning to the Kremlin about respecting Ukraine’s sovereignty, in an effort to preclude a full-scale military escalation. 
 
 American officials did not directly confirm a series of public statements by senior Ukrainian officials, including the acting president, Oleksandr V. Turchynov, that Russian troops were being deployed to Crimea, where Russia has a major naval base, in violation of the two countries’ agreements there. 
 
 Mr. Obama, however, cited “reports of military movements taken by the Russian Federation inside of Ukraine,” and he said, “Any violation of Ukrainian sovereignty would be deeply destabilizing.” 
 
 “There will be costs,” Mr. Obama said in a hastily arranged statement from the White House. 
 
 The pointed warning came after a day in which military analysts struggled to understand a series of unusual events in Crimea, including a mobilization of armored personnel carriers with Russian markings on the roads of the region’s capital, Simferopol, and a deployment of well-armed, masked gunmen at Crimea’s two main airports. 
 
 Continue reading the main story Video 
 
 “The Russian Federation began an unvarnished aggression against our country,” Mr. Turchynov said in televised remarks on Friday evening. “Under the guise of military exercises, they entered troops into the autonomous Republic of Crimea.” 
 
 He said that Russian forces had captured the regional Parliament and the headquarters of the regional government, and that they had seized other targets, including vital communications hubs, as well as blocked unspecified Ukrainian military assets. 
 
 American officials said they believed that unusual helicopter movements over Crimea were evidence that a military intervention was underway, but cautioned that they did not know the scale of the operation or the Russians’ motives. 
 
 Russia on Friday denied that it had encroached on Ukrainian territory or would do so. After an emergency meeting on Ukraine at the United Nations Security Council, the Russian ambassador, Vitaly I. Churkin, said that any troop movements were in line with arrangements that allow it to station soldiers in the area. 
 
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 “We have an agreement with Ukraine on the presence of the Russian Black Sea fleet and we operate under this agreement,” Mr. Churkin said. 
 
 Still, the developments in Crimea sent Ukraine’s interim government, which was appointed recently, deep into crisis mode as it confronted the prospect of an armed effort to split off Crimea, an autonomous region with close historic ties to Russia, from the Ukrainian mainland. 
 
 Analysts said the reported moves in the area had parallels to steps Russia took before a war with Georgia in 2008 over the largely ethnic Russian regions of Abkhazia and South Ossetia. There was little to indicate if President Vladimir V. Putin intended to escalate the challenge to Ukraine beyond nonviolent provocation of the mostly pro-Russian population in the region. 
 
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 Mr. Turchynov, the acting president, also made comparisons to Georgia. “They are provoking us into military conflict,” he said. “They began annexation of territory.” 
 
 Photo 
 
 In his address, Mr. Turchynov added, “I personally appeal to President Putin, demanding that he immediately stop the provocation and withdraw troops.” 
 
 The crisis in Crimea is the latest a series of rapidly unfurling events that began when scores of people were killed in Kiev last week during a severe escalation of civic unrest that had been underway since late November. 
 
 Protests started after Russia pressured Viktor F. Yanukovych, then the president, to back away from political and free-trade agreements with the European Union that he had long promised to sign, setting off an East-West confrontation reminiscent of the Cold War. 
 
 After the recent killings, Mr. Yanukovych reached a tentative truce with opposition leaders in talks brokered by the foreign ministers of France, Germany and Poland, but within 24 hours he fled Kiev, Ukraine’s capital, and an overwhelming majority of lawmakers voted to strip him of power, saying he had abandoned his position. 
 
 On Friday, a week later, Mr. Yanukovych resurfaced for a news conference in Rostov-on-Don, Russia, in which he said he was still the legitimate president and urged Russia not to intervene militarily in Crimea. 
 
 Mr. Obama’s warning suggested a deepening uncertainty among American officials about Mr. Putin’s intentions in the region despite a series of high-level contacts in recent days, including a telephone call between the two presidents one week ago. Mr. Yanukovych was an ally of Russia, and his toppling has left the Kremlin grappling for a response. 
 
 While American officials said that intelligence indicated that a Russian operation was underway, Mr. Obama stopped short of calling it an invasion. Part of the confusion, one official said, was that Russia routinely moves troops between military bases in Crimea. 
 
 Another American official said that intelligence reports from the region were “all over the place,” but that the administration believed that Russia had moved some of its forces into Ukraine, while some of the movement, officials said, seemed to be an increase in protective measures around Russian military installations. 
 
 Continue reading the main story Rostov-on-Don 50 Miles Don River UKRAINE Sea of Azov RUSSIA CRIMEA Simferopol Airport Simferopol Belbek Airport Sevastopol Black Sea 
 
 Though he threatened an unspecified cost to Russia, Mr. Obama has limited options to respond to an intervention. Officials said he could cancel his participation in a Group of 8 meeting in Sochi, Russia, in June. The administration could also break off talks on a potential trade agreement. Russia sent a delegation to Washington this week to explore closer trade and commercial ties. 
 
 Crimea, a multiethnic region that was granted a large degree of autonomy after Ukraine gained independence from the Soviet Union, has long been a source of tension with Russia and is home to some of Russia’s most important military installations, including the headquarters of its Black Sea naval fleet. 
 
 As other nations reacted with consternation to the developments in Crimea, the Kremlin was largely silent. 
 
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 Russian state television reported that Russian troops had arrived to secure the airport at Belbek, which is close to the Russian naval base, but officials did not confirm that information. The identity of gunmen who appeared at the Simferopol airport and at roadblocks on major roadways also remained unclear. 
 
 While movement of Russian military vehicles, equipment and personnel is common in the Crimea, Friday’s activity was extremely unusual, local residents said. It involved a number of strange components, including the deployment of heavily armed soldiers, wearing uniforms with no identifying marks, at the region’s two main airports. 
 
 Before dawn, at Simferopol’s international airport, the soldiers initially posted themselves outside an administrative building, and through much of the day they did not interfere with departing or arriving flights. 
 
 By evening, however, the usual flight in from Kiev was canceled, and it was unclear whether any flights would go through Crimean airspace over the weekend. Similarly mysterious gunmen also appeared at the second airport, which is used for civil and military flights. 
 
 Journalists spotted a convoy of nine Russian armored personnel carriers on a road between the port city of Sevastopol, the site of Russia’s main naval base, and Simferopol, a city of about 250,000 people. There were also unconfirmed reports that several planes carrying thousands of Russian soldiers had arrived in Crimea on Friday night. 
 
 Even more unusual, a Ukrainian telecommunications company, Ukrtelecom, said unknown people had seized control of several communications hubs, disrupting telephone and Internet service between Crimea and the rest of Ukraine. In a statement, the company pleaded with law enforcement agencies to take control of the situation. 
 
 While Western governments at first seemed hesitant to draw conclusions, officials in the new provisional government in Kiev said early Friday morning that they suspected Russian interference. 
 
 Mr. Turchynov, who is also the speaker of Parliament, immediately convened a meeting of the newly formed National Security and Defense Council to discuss the events in the south. ||||| 1 of 10. Armed men stand inside the regional parliament building in the Crimean city of Simferopol February 27, 2014 in this still image taken from security camera footage. Footage from security cameras shows the moment armed men seized Simferopol's parliament building in Ukraine's Crimea region on Thursday. 
 
 SIMFEROPOL, Ukraine (Reuters) - Armed men took control of two airports in the Crimea region on Friday in what the new Ukrainian leadership described as an invasion by Moscow's forces, and ousted President Viktor Yanukovich surfaced in Russia after a week on the run. 
 
 Yanukovich said Russia should use all means at its disposal to stop the chaos in Ukraine as tension rose on the Black Sea peninsula of Crimea, the only region with an ethnic Russian majority and the last major bastion of resistance to the overthrow of the Moscow-backed leader. 
 
 Acting President Oleksander Turchinov accused Russia of open aggression and said Moscow was following a scenario simliar to the one before it went to war with fellow former Soviet republic Georgia in 2008. 
 
 A day after gunmen seized the Ukrainian parliament and raised the Russian flag, a representative of Turchinov in Crimea said 13 Russian aircraft had landed on the Black Sea peninsula with 150 personnel on board each one. 
 
 More than 10 Russian military helicopters flew over Crimea and Russian servicemen blockaded a unit of the Ukrainian border guard in the port city of Sevastopol, the guard said. 
 
 A serviceman at the scene confirmed to Reuters he was from Russia's Black Sea Fleet, part of which is based in Sevastopol, and said they were there to stop the kind of protests that ousted Yanukovich in Kiev. 
 
 Some witnesses also reported seeing Russian armored personnel carriers and at least one warship on patrol. 
 
 The fleet denied its forces were involved in seizing the military airport near Sevastopol, where armed men later also occupied the runway, and a supporter described the armed group at the civilian international airport in Simferopol as Crimean militiamen. Ukraine's commercial airline said later that it had been refused entry into Crimean airspace. 
 
 Moscow has promised to defend the interests of its citizens in Ukraine. It has said it will not intervene by force, but its rhetoric since the removal of Yanukovich a week ago has echoed the run-up to its invasion of Georgia. 
 
 Any armed confrontation in Crimea would have major global repercussions, with Russia and the West already at odds over the change of power in Ukraine and supporting opposite sides in Syria's civil war. They have, however, pledged to cooperate to prop up Ukraine's faltering economy. 
 
 The U.N. Security Council called an emergency session for later on Friday at the request of Ukraine's new leaders, who warned the country's territorial integrity was threatened. Turchinov said he would not give in to "provocations". 
 
 KREMLIN ROLE 
 
 Ukraine's top security official, Andriy Paruby, said the armed men in Crimea were taking their orders from the top in Russia. "These are separate groups ... commanded by the Kremlin," Paruby, secretary of the National Security and Defence Council, told a televised briefing in Kiev. 
 
 One of the options being considered was declaring a state of emergency in Crimea, he added. 
 
 The United States warned all parties not to inflame the situation and said it had raised the issue of the reported armed takeovers of the airports with Russia. U.S. officials were seeking clarification of the origin of the armed men. 
 
 U.S. Secretary of State John Kerry said Moscow, which put 150,000 troops on high alert on Wednesday for war games near Ukraine's border, had told him it had no intention of violating Ukraine's sovereignty. 
 
 Russian Foreign Minister Sergei Lavrov said Ukraine's new leaders should implement a political deal brokered by the European Union before Yanukovich's ouster. 
 
 The Russian Foreign ministry said on its Facebook page that Russia's Consulate General in Crimea would hand out Russian passports to the servicemen of Ukraine's now-disbanded Berkut riot police. Protestors had accused the Berkut of firing the live bullets that killed dozens of protesters in Kiev. 
 
 ALL MEANS 
 
 Yanukovich - who is wanted by the new, pro-Europe government for mass murder after the protesters' deaths - reappeared in the Russian city of Rostov-on-Don. The new authorities in Kiev started moves to seek his extradition. 
 
 Yanukovich said he had not seen Russian President Vladimir Putin but had spoken to him by telephone and was surprised the Russian leader was not more vocal on the crisis. 
 
 "Russia cannot be indifferent, cannot be a bystander watching the fate of as close a partner as Ukraine," Yanukovich told a news conference. "Russia must use all means at its disposal to end the chaos and terror gripping Ukraine." 
 
 He denied he had run away, saying he had been forced to leave Kiev due to threats and denounced "lawlessness, terror, anarchy and chaos" in the country and said he had not ordered the shooting of demonstrators that preceeded his fall. 
 
 Switzerland, Austria and Liechtenstein moved to freeze assets and bank accounts of up to 20 Ukrainians including Yanukovich and his son. Yanukovich said talk of foreign bank accounts was "empty chatter". 
 
 Ukraine's new rulers have said loans worth $37 billion went missing from state accounts during Yanukovich's three years in power - a jaw-dropping sum even for a population now used to tales of a lavish lifestyle and opulent residence outside Kiev. 
 
 The new Ukrainian leadership has said the country needs almost as much as that - $35 billion - over the next two years to stave off bankruptcy. It said on Friday it hoped to get financial aid soon and was prepared to fulfill the reform criteria of the International Monetary Fund to get it. 
 
 IMF chief Christine Lagarde said she did not see anything on the economic front worthy of panic and urged the leadership to refrain from throwing numbers about she said were meaningless until properly assessed. 
 
 ARMED INVASION 
 
 Interior Minister Arsen Avakov accused Russian naval forces of taking over a military airport near the port of Sevastopol, where the Black Sea fleet has a base, and other Russian forces of seizing Simferopol's civilian international airport. 
 
 "I consider what has happened to be an armed invasion and occupation in violation of all international agreements and norms," Avakov said on his Facebook page. 
 
 This met with a Russian naval denial of involvement in the military airport action. "No Black Sea Fleet units have moved toward (the airport), let alone taking any part in blockading it," Interfax quoted a spokesman for the fleet as saying. 
 
 Near the military airport, half a dozen men in camouflage uniforms with automatic rifles were blocking the road using a truck with no license plates. Reporters were kept from approaching them by volunteer militia, who formed a second road block about 150 meters away. 
 
 "Of course they are Russian," said Maxim Lovinetsky, 23, one of the volunteers. "They came last night." 
 
 Firebrand Russian nationalist Vladimir Zhirinovsky appeared in Sevastopol where a crowd outside the city administration gave him a hero's welcome, shouting "Russia, thank you!". 
 
 "If the people have a right to rise up in a revolt and overthrow the authorities, why doesn't Sevastopol have a right to do that?" he told them. Although nominally part of the Russian opposition, he is widely seen as a servant of Kremlin policy, used to float radical opinions to test public reaction. 
 
 AVOIDING PROVOCATIONS 
 
 The United States has told Russia to show in the next few days that it is sincere about a promise not to intervene in Ukraine, saying using force would be a grave mistake. 
 
 The Kremlin said Putin had ordered his government to continue talks with Ukraine on economic and trade relations and to consult foreign partners including the International Monetary Fund on financial aid. 
 
 Yanukovich provoked protests in Ukraine in November by backing out of plans to sign landmark deals with the European Union and instead saying Kiev would seek closer economic and trade ties with its former Soviet master Russia. 
 
 Ukraine's hryvnia rose on Friday from historic lows after the central bank governor limited access to foreign currencies. Dealers said the hryvnia was trading around 9.80-10.10 to the dollar after weakening as far as 11.20-10.10 on Thursday. The hryvnia had been in freefall as investors worried about Kiev's ability to repay its debts. 
 
 Kiev's new rulers have said any movement by Russian forces beyond the base in Sevastopol would be tantamount to aggression. But they face a major challenge in Crimea which was Russian territory until it was transferred to Ukraine in 1954, during the Soviet era. Separatism there has often flared up at times of tension between Moscow and Kiev. 
 
 Armed men took control of Simferopol airport overnight and a Reuters eyewitness said the men, dressed in full battle gear and carrying assault rifles and machine guns, were moving freely in and out of the control tower. 
 
 A man called Vladimir, who said he was a volunteer helping the group, said: "We're simple people, volunteers ... We're here at the airport to maintain order." 
 
 (Additional reporting by Piotr Pilat in Simferopol, Natalia Zinets and Pavel Polityuk in Kiev, Silke Koltrowitz in Zurich, Michael Shields, Derek Brooks and Fredrik Dahl in Vienna, Brian Love in Paris and Alexei Anishchuk and Elizabeth Piper in Moscow; writing by Timothy Heritage, Richard Balmforth and David Stamp; editing by Will Waterman and Philippa Fletcher)
– More ominous developments in Crimea: Armed men have blockaded two airports in the peninsula, a day after pro-Russian gunmen took control of the regional parliament building. There are conflicting reports on who the airport gunmen are and whether they have actually taken control of the airports. At the airport in Simferopol, the Crimean capital, dozens of gunmen in unmarked military uniforms have been seen patrolling the area. "We are checking to make sure that no radicals come to Crimea from Kiev, from the Ukraine," one gunman told reporters. Flights there appear to be operating normally, CNN finds, but the Wall Street Journal reports that the other airport, Sevastopol's Belbek Airport, has been closed. Ukraine's interior minister blames Russian military units, calling this "a military invasion and occupation," the AP reports. More from Ukraine: Ethnic Russians are a majority in the Ukrainian region, which is home to Russia's Black Sea fleet, and the US has told Russia to show it is sincere about its promise not to intervene militarily, Reuters reports. "We believe that everybody now needs to take a step back and avoid any kind of provocations," John Kerry said. Ukraine's parliament also passed a resolution today demanding Russia cease any activity that could be considered an attack, CNN reports. Ousted Ukrainian leader Viktor Yanukovich, meanwhile, has surfaced in Russia, still proclaiming himself to be Ukraine's legitimate president. At a press conference today held in a Russian city near the Ukraine border, he insisted he was "not overthrown" but was forced to flee Ukraine in fear for his life, the BBC reports. He called the current parliament "illegitimate" and promised to continue fighting "against terror and fear." In Simferopol, it's not clear whether gunmen are still in control of the regional parliament building, though what the New York Times calls a "well-orchestrated power grab by pro-Russian forces" appears to have taken place across the city. Legislators held a session after the building was occupied and voted to hold a referendum this May that will decide whether to declare Crimea sovereign. CNN says the government buildings in Simferopol were still "under siege" today.