ZAWIYAH, Libya — For the first time in months, witnesses in Tripoli reported heavy fighting across the capital late Saturday night, even as rebel forces claimed to have encircled the city by taking major towns to its east, west and south. 
 
 Rebel leaders in Tunis and eastern Libya hailed the beginning of a new uprising in the capital against Col. Muammar el-Qaddafi’s rule. And after months of rebel offenses that crumbled or stalled despite heavy support from a NATO airstrike campaign, it was the first time since the uprising began in February that the rebels threatened Colonel Qaddafi’s ultimate stronghold. 
 
 “We are coordinating the attacks inside, and our forces from outside are ready to enter Tripoli,” said Anwar Fekini, a rebel leader from the mountainous region in western Libya, speaking by telephone from Tunis. “If you can call any mobile number in Tripoli, you will hear in the background the beautiful sound of the bullets of freedom.” 
 
 Phone calls to several Tripoli residents from different neighborhoods confirmed widespread gunfire and explosions. And there were reports of frequent NATO jet overflights and airstrikes — a common accompaniment to the drumbeat of the rebel advance in the past week. 
 
 But in an audio message broadcast on state television, his second in a week, Colonel Qaddafi rejected claims of rebel gains, saying his forces had beaten back the Tripoli uprising within hours and announcing military successes in the same cities rebels had claimed to seize on Saturday. He gave the date and time several times to confirm that he was speaking as events were unfolding. 
 
 “The rebels are fleeing like rats, to the mountains,” Colonel Qaddafi said. 
 
 But even as he described a “collapse” among rebel fighters and NATO forces, he railed at world leaders who were supporting the uprising, accusing them of giving rebels “weapons to destroy our air-conditioners!” 
 
 He gave no indication of where he might be speaking from, a topic of increasing speculation in recent days as rumors have swirled of his preparing to flee, or perhaps having already left Libya. 
 
 If Colonel Qaddafi’s location remained unknown, it became increasingly clear Saturday that even his most senior aides were making exits of their own. 
 
 The Tunisian state news agency reported Saturday that Libya’s oil minister, Omran Abukraa, had defected to Tunisia, after leaving Tripoli on what was ostensibly a business trip abroad. If confirmed, his defection would be the third of a senior government official in the past week. 
 
 Abdel Salam Jalloud, a former Qaddafi deputy, was reported to have defected Friday. A senior security official, Nassr al-Mabrouk Abdullah, flew to Cairo with his family on Monday. 
 
 Mustafa Abdel-Jalil, the chairman of the rebel government, the National Transitional Council, said that he hoped Colonel Qaddafi and the rest of his inner circle would follow. “That would be a good thing that will end the bloodshed and help us avoid material costs,” he said. “But I do not expect that he will do that.” 
 
 After reports of the Tripoli fighting began, some residents said that a group of rebel fighters had infiltrated the city from the east and were spearheading the uprising, surprising the pro-Qaddafi forces who had fortified for an attack from the western approach guarded by Zawiyah. Residents added that in recent weeks rebels had also smuggled weapons into the city by boat to the beaches east of Tripoli to prepare. Their claims could not be independently confirmed. 
 
 Meanwhile, rebel forces closing in on the capital made important gains on Saturday. By afternoon, the rebels had driven Colonel Qaddafi’s forces out of Zawiyah, the strategic oil refinery town 30 miles west of Tripoli. After a week of heavy fighting there, residents began to celebrate in the main square. 
 
 The Arab news network Al Jazeera reported that Zlitan, a crucial Qaddafi barracks town east of Tripoli, also had fallen to the rebels. They captured Gharyan, the gateway to the south, last week. 
 
 Farther east, the rebels claimed to have seized the residential areas of the oil port of Brega, a prize that has changed hands many times since the uprising began. 
 
 A senior American official said Colonel Qaddafi’s days “are numbered.” ||||| Libyan rebels launched an assault early Sunday on the capital of Tripoli amid unconfirmed reports that leader Moammar Gadhafi had fled, NBC News reported. 
 
 "Zero hour has begun," a rebel commander told NBC News. 
 
 However, a government spokesman said Gadhafi remained in control and the leader in a live interview on state television called the rebels "rats" who need to be destroyed. 
 
 Rebels were fighting in at least four areas of Tripoli, NBC News said. 
 
 Four loud explosions were heard at around 4 a.m. Sunday local time in the heart of the city as NATO warplanes flew overhead, Sky News reported. The targets have not yet been identified. 
 
 Earlier Sunday protesters demanding the departure of Gadhafi took to the capital streets, Reuters said. Heavy mortar fire and sustained gunfire grew intense, witnesses said. 
 
 White House and U.S. intelligence officials were monitoring rumors that Gadhafi had left with his two sons, Hannibal and Mutassim, ending his 41-year rule, NBC News reported. 
 
 Late last week, intelligence officials told NBC News that Gadhafi might seek exile in Tunisia. 
 
 White House officials said President Barack Obama, vacationing at Martha's Vineyard, Mass., "had been briefed on Libya and is getting regular updates as needed." 
 
 A second senior official said the administration was in close contact with the Libyan opposition and U.S. allies and partners, and believes that Gadhafi's days in power are numbered. Both aides spoke on condition of anonymity. 
 
 In Libya, rebels said they launched the Tripoli assault in coordination with NATO and with the uprising of rebels inside the capital. 
 
 "This was a pre-set plan," said Abdel Hafiz Ghoga, vice-chairman of the National Transition Council, based in the eastern Libyan city of Benghazi. "They've been preparing for a while. There's coordination with the rebels approaching from the east, west and south.'' 
 
 Ghoga said NATO warplanes were launching raids to distract Gadhafi's forces. 
 
 "The next hours are crucial. Many of their (pro-Gadhafi) brigades and their commanders have fled.'' 
 
 His claims could not be independently confirmed immediately. 
 
 Sustained gunfire and thuds were heard in the distance and residents of Tajoura, on Tripoli's eastern outskirts, where reported clashes were under way. 
 
 An eyewitness told Al Arabiya news agency that the suburb was in rebel hands and people were out dancing in the streets. 
 
 Free Libya Now television reported that rebel forces set up command and control and civil control structures. 
 
 It also claimed rebels were in control of the airport, but the government denied the report. 
 
 An unknown number of rebels were killed in clashes in the Tripoli suburb of Qadah and fighting was ongoing at Mitiga airbase, a rebel activist told Reuters. 
 
 In the eastern coastal city of Benghazi, residents took to the streets to celebrate the advance on Tripoli, Al Jazeera news agency reported. 
 
 However, Gadhafi on a state television audio broadcast, congratulated Libyans on the elimination of "the rats." 
 
 He said French President Nicolas Sarkozy "wants the Libyan oil." Rebels don't represent Libya and are bent on "the destruction of the Libyan people," he said, also mentioning the time so he could prove his statements were not pre-recorded. 
 
 He signed off saying, "Long live. Go forward, go forward, go forward, go forward." 
 
 Gunfire was heard in Tripoli after Gadhafi finished his talk, witnesses said. ||||| TRIPOLI Explosions and gunfire rocked Tripoli overnight, after days of battlefield defeats left Muammar Gaddafi's government and troops penned ever more tightly in the besieged capital. 
 
 The fighting inside the city triggered celebrations among some rebels and speculation Gaddafi's 41-year rule was sliding toward collapse. But Gaddafi's officials insisted in the early hours of Sunday the assault had been crushed, a few hours after it began. 
 
 Government spokesman Moussa Ibrahim said small groups of armed rebels had infiltrated the capital but had been dealt with. 
 
 "I assure Libyans that Gaddafi is your leader ... Tripoli is surrounded by thousands to defend it," he said. 
 
 Fighting was still raging around Mitiga airbase in Tripoli's Tajourah district after midnight, an opposition activist told a Reuters journalist outside Libya. The gunbattles had left a number of rebels dead in the suburb of Qadah and elsewhere, he said. 
 
 Earlier on Saturday evening, residents told Reuters of gunfire and street protests in several parts of Tripoli. 
 
 "We can hear shooting in different places," said one. "Most of the regions of the city have gone out, mostly young people ... it's the uprising... They went out after breaking the (Ramadan) fast." 
 
 "They are shouting religious slogans: God is greatest!" 
 
 Residents said in the early hours of Sunday that shooting appeared to be subsiding, about four hours after it began. 
 
 This week's rebel advances on Tripoli have transformed the war by cutting the capital off from its main road link to the outside world and putting unprecedented pressure on Gaddafi. 
 
 DEFECTIONS 
 
 Washington says his days are numbered, and reports have emerged of more defections from his ranks. President Barack Obama, on vacation in Martha's Vineyard, was receiving regular updates on Libya, a senior White House official said. 
 
 The six-month-old war came close to the Tunisian frontier after rebels suddenly seized the coastal city of Zawiyah just 50 km (30 miles) west of Tripoli, surrounding the heavily fortified capital and severing its vital supply routes. 
 
 In Tunisia, security sources said their forces had intercepted Libyan men in vehicles with weapons and fought them through the night in the desert. They reported several casualties, but did not say whether the fighters were Libyan rebels or pro-Gaddafi soldiers cut off from Tripoli. 
 
 Residents of the southern Tunisian desert town of Douz told Reuters by telephone that helicopters were swooping overhead and troops had been summoned from nearby towns to subdue the infiltrators, who rode in vehicles without number plates. 
 
 The imposition of a siege around Tripoli has trapped its residents and cut it off from fuel and food supplies. The International Organization for Migration said on Friday it would organize a rescue operation to evacuate thousands of foreign workers, probably by sea. 
 
 Intense fighting continued in Zawiyah, home to an important oil refinery, on Saturday and rebels occupying the center of the city said pro-Gaddafi forces showed no sign of retreat. 
 
 "Gaddafi will try to take back Zawiyah at any price. He will keep shelling the hospital," said a rebel fighter as he prepared for midday prayers in the mosque of Bir Hawisa, a nearby village where many civilians are sheltering. 
 
 "We will not let that happen. We will fight." 
 
 East of Tripoli, fighting has been bloodier and rebel advances far slower. On Friday, opposition forces fought street battles in the city of Zlitan but suffered heavy casualties, a Reuters reporter said. A rebel spokesman said 32 rebel fighters were killed and 150 wounded. 
 
 NATO BOMBINGS 
 
 NATO warplanes have hammered Gaddafi military targets since March under a U.N. mandate to protect civilians. Gaddafi's government has said the bombs have killed scores of innocent people, including 27 during a raid on Tripoli this week. 
 
 On Saturday, Libyan Prime Minister Al Baghdadi Ali Al-Mahmoudi spoke to U.N. General Secretary Ban Ki-moon by telephone requesting an investigation into alleged abuses by NATO, Libyan state news agency JANA reported. 
 
 JANA said Ban had promised to study the proposal. 
 
 In another potential blow to Gaddafi, a Tunisian source said Libya's top oil official, Omran Abukraa, had arrived in Tunisia after deciding not to return to Tripoli from a trip to Italy. 
 
 If confirmed, it would be the third apparent defection of a senior Gaddafi associate this week. A senior security official arrived in Rome on Monday, and rebels said on Friday that Gaddafi's estranged former deputy Abdel Salam Jalloud had joined their side in the western mountains. 
 
 The siege of Tripoli and the prospect of a battle for the capital have added urgency to the question of Gaddafi's fate. The leader has repeatedly vowed never to leave the country and rebels say they will not stop fighting until he is gone. 
 
 A senior U.S. official said on Saturday that the opposition must prepare to take over power soon. The United States is among more than 30 nations that have recognised the rebels' National Transitional Council (NTC) as Libya's legitimate authority. 
 
 "It is clear that the situation is moving against Gaddafi," U.S. assistant Secretary of State Jeffrey Feltman told a news conference after meeting Libyan rebel leaders at their headquarters in Libya's eastern city of Benghazi. 
 
 "The opposition continues to make substantial gains on the ground while his forces grow weaker." 
 
 (Additional reporting by Missy Ryan in Tripoli and Robert Birsel in Benghazi, Libya; Souhail Karam in Rabat, Morocco; Writing by Richard Valdmanis and Peter Graff; Editing by Andrew Roche)
– It looks like Libyan rebels are closing in for the kill: Reuters reports heavy gunfire and explosions in Tripoli. Rebels have made swift progress this week knocking off strategic cities around the capital, and now it, too, looks in danger of falling. Residents tell the news agency that people are in the streets in some areas shouting anti-Gadhafi slogans. A government spokesman, however, took to state television to downplay the unrest: "All of Tripoli is safe and stable." Even if that's true, it probably won't be for long, a US assistant secretary of state tells the New York Times. “It is clear that the situation is moving against Gadhafi," says Jeffrey D. Feltman. "The opposition continues to make substantial gains on the ground while his forces grow weaker.” Already, rumors are circulating that Gadhafi himself has fled Tripoli, reports NBC News, but there's no confirmation. Earlier reports had him poised to leave for Tunisia.