"Twelve air strikes hit multiple areas in Douma," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, a war monitor based in Britain.

"Four civilians were killed and around 25 wounded," he told AFP.

They were the first bombing raids on Douma since negotiations began around 10 days ago over a withdrawal of rebels and civilians from the town, the largest in Eastern Ghouta.

Backed by Russia, Syrian troops have recaptured 95 percent of Ghouta since February 18 through a combination of a deadly air and ground assault and evacuation deals.

Moscow had announced a deal with Jaish al-Islam, the Islamist faction that holds the town, but hardliners within the group were reportedly refusing to leave their positions.

Syria and Russia had threatened a resumption of their brutal assault if Jaish al-Islam did not agree to the deal.

Syria's state news agency SANA said Syrian air strikes hit the town on Friday in response to rebel mortar fire from Douma that wounded seven people near the capital.