More than 100 000 have died since the start of the conflict, the United Nations says, and millions more have been displaced. (REUTERS)
Islamist rebels retook most of a military base in northern Syria from forces loyal to President Bashar al-Assad on Saturday after two days of fighting in which at least 60 people have been killed, a monitoring group said.
The heavy fighting reflects the strategic importance of the 80th Brigade army base, a few hundred metres from Aleppo airport on the eastern approaches of the disputed city. Rebels had held the site for nine months until Friday when Assad's troops, backed by heavy artillery fire and air strikes, briefly pushed them out.
The Syrian Observatory for Human Rights said fighting continued on Saturday around the base, one of several locations to the east and southeast of Aleppo where Assad's forces have been challenging rebel control.
The army has recaptured the town of Safira, where one of Syria's main chemical weapons facilities was housed, and has advanced to attack the rebel-held towns of Tel Arn and Tel Hasel which are closer to the southeastern edge of Aleppo.
If it were to take those towns and the army base, authorities would have tightened their control around the airport, which has been closed to most civilian flights after rebels fired at an airliner there last December.
Rami Abdelrahman of the British-based Observatory, which monitors the violence in Syria through a network of medical and security sources, said at least 21 soldiers and 41 rebels - including 11 foreign fighters from the Islamic State in Iraq and the Levant - had been killed in fighting for the base.
He said the army was backed by the Lebanese Shi'ite militant group Hezbollah and pro-Assad Syrian militias. State media made no reference to the fighting around the army base, but said a rocket-propelled grenade fired by rebels killed six children in the Ashrafiyeh district of Aleppo.
Once Syria's most populous city and commercial hub, Aleppo has been divided roughly in half by the warring parties. Rebels hold most of Aleppo province but the government wants to keep a foothold in the north, where rebel supplies flood in from Turkey.
Assad's forces also took the strategic southern town of Sbeineh near Damascus on Thursday, threatening rebel control of the wider area and cutting off a supply route for insurgents around the capital.
After 2-1/2 years of war, which started when Assad's forces fired on pro-democracy protests, the fighting has settled into a broad stalemate in which more than 100 are killed every day. More than 100 000 have died since the start of the conflict, the United Nations says, and millions more have been displaced.