The Syrian Observatory for Human Rights also reported five people killed in regime barrel bomb raids in the Aleppo region in the north, taking to 82 the civilian death toll in such attacks in the province this week.
Around the capital, the air force carried out five raids on Arbin in Eastern Ghouta, killing the 12 who included three women and two children, and wounding dozens, the Britain-based Observatory said.
It also said helicopters dropped 28 barrel bombs in the Zabadani area, the last rebel bastion near the border with Lebanon.
Syrian government forces backed by fighters from Lebanon's Shiite Hezbollah militia have been on the attack in the Zabadani area for the past week.
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Zabadani, 47 kilometres (29 miles) northwest of Damascus on the road to Beirut, is strategic to Hezbollah and rebels have been under siege there for more than two years.
Many residents have left as stocks of food and medicines dried up because of the siege, but activists say there are still a few thousand civilians there, mostly in eastern districts.
For more than a week government forces have been targeting Al-Bab which is controlled by the jihadist Islamic State group.