Shelling and aerial raids by Syrian government forces killed at least 20 civilians on Saturday in Douma, a rebel-held town east of Damascus, a monitoring group said.

"At least 20 civilians were killed in the heavy shelling and air attacks since this morning on Douma," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.

He said about 200 others were either wounded or still trapped under the rubble. On Sunday, regime attacks on the same town killed more than 100 people.