By . Mario Ledwith . PUBLISHED: . 20:58 EST, 1 January 2013 . | . UPDATED: . 06:52 EST, 2 January 2013 . Escalating violence between between government troops and rebel fighters forced authorities to close the airport in Aleppo, Syria's largest city. Rebels have stepped up their attacks on airports in the province in an attempt to curb deadly air strikes by President Bashar Assad's forces. The Government-backed air force has been targeting rebel positions in recent weeks and attacking towns under opposition control. Scroll down for video . Ravaged: The burned out remains of an emergency vehicle in Aleppo, where violence has escalated in recent weeks with rebels specifically targeting Government-controlled air bases . Fatal: Fighting in Aleppo has intensified with rebel forces specifically targeting air bases. The Britain-based Syrian Observatory for Human Rights said fighting led to closure of Aleppo International Airport on Monday . The rebels have been attacking three . other airports in the Aleppo area, including a military helicopter base . near the Turkish border. Videos online appear to show fighters shooting mortars, homemade rockets and sniper . rifles at targets inside the bases. Assad's ability to attack from above poses one of the biggest obstacles to rebel forces, who have much more limited weaponry and military capabilities. The rebels' attempts to capture Aleppo have led to an increase in violence in the embattled country, which has been locked in civil war for 21 months as opposition forces try to overthrow authoritarian leader Assad. The bloody war has resulted in almost 40,000 deaths so far. Control of Aleppo is seen as a key element of the war and rebel forces have been attempting to take control of the city since the summer, having captured large swathes of territory in the province west and north of the city. Concern: A girl looks up to the sky after hearing the sound of shelling in Aleppo. Rebels have stepped up their attempts to overthrow President Bashar Assad's forces in the city . Isolated: Children sit on school benches at Al-Tawheed school in Aleppo. The city has been a focal point of the bloody war in Syria that has reportedly killed 40,000 people . The Britain-based Syrian Observatory for Human Rights, an anti-regime activist group, said the fighting around the base of Syrian army Brigade 80, part of a force protecting Aleppo International Airport, led to the closure of the airport late Monday. 'Heavy fighting is taking place around Brigade 80,' said Rami Abdul-Rahman, who heads the Observatory. 'The airport has been closed since yesterday,' he said. The Syrian government did not comment on the closing of the airport. Syria's national airline also canceled a flight to Aleppo because of fighting nearby on Saturday. Rebels have warned that they would target civilian as well as military planes using the Aleppo airport, saying the regime is using civilian planes to bring in supplies and weapons. There has also been heavy fighting in the Damascus suburb of Daraya, southwest of the capital. Threat: Rebel fighters launched a major offensive on Aleppo in mid-July but the city had remained in stalemate until recent weeks . Desperate: Children cutting a tree branches at a public park to be used for heating in Aleppo . Daraya is one of the closest suburbs to the capital and is on the edge of two important neighborhoods that are home to a strategic air base and government headquarters. Although the regime still tightly controls much of Damascus, its seat of power, rebels have been posing a stiffer challenge in the suburbs. In the past few weeks, there has been fighting near the capital's international airport that interrupted some flights. The road to the airport, just south of the capital, was also closed during the fighting. The Observatory and activist Mohammed Saeed, who is based near Damascus, said Syrian warplanes bombed Daraya on Tuesday. State-run news agency SANA said troops killed 'tens of terrorists' in Daraya and nearby areas. The regime refers to rebels as 'terrorists.' Keeping warm: Boys collect wood to be used for fire in Aleppo as winter threatens the city's impoverished and homeless . 'The regime is doing all it can to regain Daraya. The regime is dying to get back it back,' said Maath al-Shami, an activist based in the Syrian neighborhood of Mazzeh. He added: 'Daraya is the gate of Damascus for the rebels.' Amateur videos showed smoke billowing from Daraya from what activists said were the air raids. Another video showed a street covered with debris as fire raged on the second floor of a five-story building. In August, activists reported that between 300 and 600 people were killed in Daraya over several days in a killing spree by troops and pro-regime militiamen who stormed the town after heavy fighting and days of shelling. The Observatory and al-Shami reported sporadic shelling and clashes in southern neighborhoods of Damascus and the Palestinian refugee camp of Yarmouk on Tuesday. The Observatory said shelling and snipers fire killed two people in Yarmouk and two in another neighborhood.
Rebel forces targeting airports in attempt to curb President Assad's air force .
Use of air strikes one of military's key advantages over opposition forces .
Civil war has raged for 21 months with a death toll of 40,000 people .
By . Mario Ledwith . PUBLISHED: . 20:58 EST, 1 January 2013 . | . UPDATED: . 06:52 EST, 2 January 2013 . Escalating violence between between government troops and rebel fighters forced authorities to close the airport in Aleppo, Syria's largest city. Rebels have stepped up their attacks on airports in the province in an attempt to curb deadly air strikes by President Bashar Assad's forces. The Government-backed air force has been targeting rebel positions in recent weeks and attacking towns under opposition control. Scroll down for video . Ravaged: The burned out remains of an emergency vehicle in Aleppo, where violence has escalated in recent weeks with rebels specifically targeting Government-controlled air bases . Fatal: Fighting in Aleppo has intensified with rebel forces specifically targeting air bases. The Britain-based Syrian Observatory for Human Rights said fighting led to closure of Aleppo International Airport on Monday . The rebels have been attacking three . other airports in the Aleppo area, including a military helicopter base . near the Turkish border. Videos online appear to show fighters shooting mortars, homemade rockets and sniper . rifles at targets inside the bases. Assad's ability to attack from above poses one of the biggest obstacles to rebel forces, who have much more limited weaponry and military capabilities. The rebels' attempts to capture Aleppo have led to an increase in violence in the embattled country, which has been locked in civil war for 21 months as opposition forces try to overthrow authoritarian leader Assad. The bloody war has resulted in almost 40,000 deaths so far. Control of Aleppo is seen as a key element of the war and rebel forces have been attempting to take control of the city since the summer, having captured large swathes of territory in the province west and north of the city. Concern: A girl looks up to the sky after hearing the sound of shelling in Aleppo. Rebels have stepped up their attempts to overthrow President Bashar Assad's forces in the city . Isolated: Children sit on school benches at Al-Tawheed school in Aleppo. The city has been a focal point of the bloody war in Syria that has reportedly killed 40,000 people . The Britain-based Syrian Observatory for Human Rights, an anti-regime activist group, said the fighting around the base of Syrian army Brigade 80, part of a force protecting Aleppo International Airport, led to the closure of the airport late Monday. 'Heavy fighting is taking place around Brigade 80,' said Rami Abdul-Rahman, who heads the Observatory. 'The airport has been closed since yesterday,' he said. The Syrian government did not comment on the closing of the airport. Syria's national airline also canceled a flight to Aleppo because of fighting nearby on Saturday. Rebels have warned that they would target civilian as well as military planes using the Aleppo airport, saying the regime is using civilian planes to bring in supplies and weapons. There has also been heavy fighting in the Damascus suburb of Daraya, southwest of the capital. Threat: Rebel fighters launched a major offensive on Aleppo in mid-July but the city had remained in stalemate until recent weeks . Desperate: Children cutting a tree branches at a public park to be used for heating in Aleppo . Daraya is one of the closest suburbs to the capital and is on the edge of two important neighborhoods that are home to a strategic air base and government headquarters. Although the regime still tightly controls much of Damascus, its seat of power, rebels have been posing a stiffer challenge in the suburbs. In the past few weeks, there has been fighting near the capital's international airport that interrupted some flights. The road to the airport, just south of the capital, was also closed during the fighting. The Observatory and activist Mohammed Saeed, who is based near Damascus, said Syrian warplanes bombed Daraya on Tuesday. State-run news agency SANA said troops killed 'tens of terrorists' in Daraya and nearby areas. The regime refers to rebels as 'terrorists.' Keeping warm: Boys collect wood to be used for fire in Aleppo as winter threatens the city's impoverished and homeless . 'The regime is doing all it can to regain Daraya. The regime is dying to get back it back,' said Maath al-Shami, an activist based in the Syrian neighborhood of Mazzeh. He added: 'Daraya is the gate of Damascus for the rebels.' Amateur videos showed smoke billowing from Daraya from what activists said were the air raids. Another video showed a street covered with debris as fire raged on the second floor of a five-story building. In August, activists reported that between 300 and 600 people were killed in Daraya over several days in a killing spree by troops and pro-regime militiamen who stormed the town after heavy fighting and days of shelling. The Observatory and al-Shami reported sporadic shelling and clashes in southern neighborhoods of Damascus and the Palestinian refugee camp of Yarmouk on Tuesday. The Observatory said shelling and snipers fire killed two people in Yarmouk and two in another neighborhood.
an attempt to curb deadly air strikes by President Bashar Assad's forces. The Government-backed air force has been targeting locked in civil war for 21 months as opposition reportedly killed 40,000 people . The Daraya is one of the closest suburbs to the