Air raids by Syrian government warplanes killed 20 civilians, including seven children, in an area southeast of Damascus on Thursday, the Syrian Observatory for Human Rights monitor said.
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.
More than 250,000 people have been killed in Syria's conflict, which began in March 2011 as an anti-government protest movement but which has spiralled into a multi-sided war.