Regime and Russian air strikes on a rebel-held enclave near Damascus killed at least 17 civilians on Saturday, the Syrian Observatory for Human Rights said.
The deadliest of the raids on the Eastern Ghouta region hit the Hammuriyeh district, leaving 12 civilians dead including two children, the British-based war monitor said.
Two people were killed in the town of Madira and three in Erbin, the Observatory head added, saying 35 people were also wounded in the three areas.
Eastern Ghouta is the target of near-daily regime air raids.
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 militants 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.
More than 340,000 people have been killed in Syria and millions displaced since the conflict began in March 2011 with anti-government protests.