( CNN ) -- Violence surged in the strategically important Syrian town of Qusayr on Sunday . Activists said the offensive marked some of the most intense fighting they 've seen in the fiercely contested area near the Lebanese border . Rebels and the Syrian government both claimed to control parts of the city , where fighting has been raging for weeks . Activists said artillery shells , mortar shells and bombs from aircraft were raining down as government forces attacked . Makeshift medical clinics were reportedly filled with casualties . By all accounts , Qusayr is in a strategically valuable location . For rebels fighting President Bashar al-Assad 's government , it sits along a transit route for weapons and supplies coming in from Lebanon . For the Syrian government , it 's a key point between the capital of Damascus and al-Assad 's supporters on the Mediterranean coast . Videos posted on social media Sunday show the city blanketed with black and gray smoke amid an almost continuous stream of sounds of mortar and artillery fire . Dozens of people were killed in the clashes , including 48 rebel fighters , the London-based opposition Syrian Observatory for Human Rights reported . Hundreds of people were injured , many in critical condition , the opposition organization said . Syrian state-run television reported that Syrian forces `` have spread safety and security after taking control of the city hall and surrounding buildings in Qusayr as they continue to chase the terrorists in the city . '' The opposition Local Coordination Committee of Syria denied that report . `` The field commanders in the Free Syrian Army stress that they remain in control of the city and are fighting back attempts to storm the city , '' the opposition activist network said in a statement . Activists describe a city under siege . Qusayr has been under rebel control for months . The opposition accused Hezbollah fighters from neighboring Lebanon of joining Syrian government troops in the assault on the city , a claim that al-Assad 's government has disputed in the past . The Shiite militant group is considered a terror organization by the U.S. government and is a traditional ally of al-Assad as well as Iran . The Free Syrian Army said it fired rockets from Qusayr across the border into northeastern Lebanon , targeting Hezbollah areas . The official Lebanese news agency said eight rockets landed in Hermel . Activists in Qusayr said the city was under siege Sunday from several directions . `` There is continuous shelling using artillery , mortar and warplane bombs , '' activist Abu Ali said . `` It is so intense , like 50 shells a minute . '' Residential areas were hit , said Abulhoda Homsi , another activist . The opposition Syrian National Council warned that 40,000 civilians ' lives were in danger amid the violence and called for the Arab League to hold an emergency meeting to protect the besieged city . The United Nations estimates that more than 70,000 Syrians have been killed since anti-government protests in March 2011 led to a fierce government crackdown , an armed uprising and a civil war with no end in sight . At least 125 people were killed across the country Sunday , the Local Coordination Committees reported . How to end the civil war in Syria . The voice of Assad . In an interview with Argentine journalists on Saturday , Assad said Syria can solve its own problems . `` It is n't up to the United States or any other country to intervene , '' the Syrian president told Argentina 's Telam news agency . `` This is an issue that is Syrian . We are an independent state . We respect ourselves . We do n't accept anyone telling us what to do -- not the U.S. , not any other country . '' Assad asserted he 's dealing appropriately with people he calls `` terrorists . '' `` Nobody has dialogue with the terrorists . Terrorism has hit the United States and Europe . By any chance , did any of these governments talk to terrorists ? One talks with political entities , but not with a terrorist who cuts people 's throats , assassinates people and uses chemical weapons , '' he said , ignoring allegations that his own government has very likely used chemical weapons on Syrian citizens . Massive flight . The Syrian civil war has uprooted a quarter of the country 's civilians , according to the United Nations . The number of Syrians who have fled the violence has surpassed 1.5 million , the U.N. High Commissioner for Refugees said Friday . Since the start of 2013 alone , the UNHCR has registered close to 1 million refugees crossing out of the battered nation into other countries , which amounts to about 250,000 people each month . Along with the refugees , more than 4 million people have been internally displaced . Syria has a population of just over 22 million , according to the CIA World Factbook . Opinion : Heart-eating video raises pressure to end Syrian war . CNN 's Yousuf Basil , Samira Said and Nic Robertson contributed to this reoprt .
Rebels and the Syrian government both claim to control parts of Qusayr . Opposition activists report intense shelling , hundreds of injuries . The strategically important city has been under rebel control for months . The opposition accuses Hezbollah fighters from neighboring Lebanon of joining Syrian troops .