At least 31 civilians were killed Sunday in heavy bombardment of a besieged Syrian rebel stronghold east of Damascus that also struck a school, AFP reports.

The Syrian Observatory for Human Rights said rockets fired by regime forces rained down on Douma, one of the largest towns in the opposition-held Eastern Ghouta region.

Observatory head Rami Abdel Rahman said air strikes also hit Douma and the nearby towns of Saqba and Harasta, but it was unclear whether they were carried out by Syrian or Russian warplanes.

At least 28 civilians were killed in the bombing of Douma and Saqba, and another three civilians were left dead after the air strikes in Harasta.

Two children were among the dead, and dozens of people were wounded, he said.