Warplanes struck the rebel-held town of Douma in eastern Ghouta near Damascus on Friday, state TV and a war monitor reported, shattering days of calm as mediated talks between the sides appeared to have collapsed.
There was no immediate comment from Jaish al-Islam, the rebel group that has held out in Douma as insurgents in other parts of eastern Ghouta have accepted safe passage out to opposition-held areas at the border with Turkey.
The Syrian Observatory for Human Rights, the war monitor, said two people had been killed and 25 wounded in a dozen air raids against Douma. It said the warplanes were likely Russian.
State TV said Jaish al-Islam had shelled a crossing point out of Douma and a residential area, triggering the air strikes on a town where the Observatory said tens of thousands of people are still thought to be sheltering.
The Observatory said Russian-mediated talks between the government and Jaish al-Islam had collapsed, and Jaish al-Islam proposals for it to remain in the area as a local security force had been rejected.
State TV, in an on-screen news flash, said Jaish al-Islam was obstructing a deal and had refused to release abductees it has been holding.
The group has consistently rejected the idea of leaving Douma for areas near the Turkish border, saying this amounts to a policy of forced population transfer by President Bashar al-Assad.
Several thousand people have left Douma in convoys to the north in recent days, including wounded rebel fighters and civilians but not active Jaish al-Islam fighters, Observatory Director Rami Abdulrahman said.