Dozens more people were also wounded in the raids on the centre of Hammuriyeh in Eastern Ghouta, the largest rebel stronghold in Damascus province.
The area is regularly bombed by the forces of President Bashar al-Assad, Observatory director Rami Abdel Rahman said.
Two more civilians were also killed by shelling in the Douma area, northeast of Damascus, while government forces were also pounding Eastern Ghouta with artillery fire, the Observatory said.
Rebels often shell the capital from Eastern Ghouta, to the east of Damascus.