Regime and Russian air strikes on a rebel-held enclave near the Syrian capital killed at least 17 civilians on Saturday, a war monitor said.
Eastern Ghouta, one of the last remaining opposition strongholds in the country, is the target of near-daily air raids.
The Syrian Observatory for Human Rights said Saturday's deadliest strikes had hit the Hammuriyeh district, killing 12 civilians, including four children.
An AFP reporter in Hammuriyeh saw residential buildings with their facades blown open, collapsing into streets strewn with rubble.
Residents including members of the White Helmets rescue group rushed to rescue the wounded.
Running past a burning car, one man held a crying boy in his arms, while another carried the apparently lifeless body of a child through the streets.
"I was with other people when a projectile fell nearby," said 33-year-old Mustafa Abu Badr, who was slightly wounded in the head.
"The blast threw me five metres. There were seven wounded and one dead," he said.
Observatory head Rami Abdel Rahman said Syrian and Russian aircraft had "continued their intense bombardment of Eastern Ghouta, targeting several residential areas".
He said those killed also included two people in the district of Madira and three in Erbin, and that 35 people were wounded in the three areas.
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The Britain-based monitor relies on a network of sources inside Syria and says it determines whose planes carry out raids according to type, location, flight patterns and munitions used.
At the start of the week, a coalition of rebels and jihadists including a former Al Qaeda affiliate surrounded the only regime base in Eastern Ghouta, which lies east of Damascus and has been under a crippling regime siege since 2013.
The blockade has caused serious food and medicine shortages for the enclave's estimated 400,000 inhabitants.
Rebels in Eastern Ghouta respond to air strikes by firing shells and rockets at Damascus. On Saturday, shellfire killed a civilian, Syrian state television reported.
More than 340,000 people have been killed in Syria and millions displaced since the conflict began in March 2011 with anti-government protests.