Syrian troops battled rebels near Damascus on Saturday and launched air strikes on opposition strongholds in the south of the capital and on its northeastern outskirts, a watchdog said.

The Syrian Observatory for Human Rights gave an initial toll of 49 people killed nationwide, including 16 civilians and 16 rebels killed in Damascus province alone.

To the northeast of the capital, seven civilians including a child were killed in heavy army shelling on the town of Misraba.

Nearby, warplanes bombarded the town of Douma and areas between Harasta and Irbin, said the watchdog, adding that 10 rebels were killed in fierce clashes with troops in the area.

The Observatory also reported three rebels and two civilians killed in shelling on southern areas of the capital, including in Daraya, where troops had launched a major military operation to try and seize control of the town.

For several days, the army has pounded rebel strongholds on the capital's outskirts, where the fighters have set up their rear bases, raising fears of a looming ground assault.

Abu Kinan, an activist in Daraya, said that clashes had broken out between the rebel Free Syrian Army and government troops to the east and west of Daraya.

"The army is getting reinforcements and has arrested more than 80 displaced people who were living in the surrounding areas, just because they are from Daraya," he told AFP via Skype.

He said that the army had not yet succeeded in entering the town, the scene in August of the single deadliest massacre of the 21-month conflict.

State television reported that the army had "destroyed a number of vehicles and motorcycles used by terrorists" in Harasta and Daraya.

The Observatory said that the army mounted attacks on rebel positions near the borders with Turkey and Israel.

Air strikes struck the northern town of Tal Abyad near Turkey, the Britain-based watchdog said, while shells fell on the villages of Bir Ajam and Al-Buraykah in the Syrian side of the Israeli-occupied Golan Heights.

In the northwestern province of Idlib, four men were killed in air strikes on the village of Kfar Lateh, and warplanes also bombed Maaret al-Numan and the nearby village of Has, killing two men and leaving 15 others wounded.

In Aleppo province in the north, warplanes pounded the towns of Aazaz and Jarablus, and targeted rebel positions around the Meng military airport which is ringed by several battalions.

More than 42,000 people have been killed since the uprising erupted in March last year, according to the Observatory, which relies on a network of activists, lawyers and medics on the ground.