At least 28 civilians were killed in heavy bombardment of a besieged rebel stronghold east of the Syrian capital on Sunday, a monitoring group said.

According to the Syrian Observatory for Human Rights, rockets fired by regime forces rained down on the opposition-held  Eastern Ghouta region. 

Observatory head Rami Abdel Rahman said air strikes also hit two towns in the region, but it was unclear whether they were carried out by Syrian or Russian warplanes.