Forty people have been killed by rockets fired by Syrian government forces into a market in a rebel-held area outside Damascus.
At least 100 people were also wounded in the attack in the centre of Douma in the city's east, the Syrian Observatory for Human Rights told news agency AFP on Friday (local time).
Head of the watchdog Rami Abdel Rahman said "there is still heavy fire now with both rockets and mortars".
Rahman added that the toll was expected to rise as people were still being pulled out of damaged buildings.
Rebel-held Douma lies in Eastern Ghouta, the largest opposition stronghold in Damascus province.
The region is regularly targeted by rocket fire, shelling and aerial raids by government forces and opposition groups there also fire rockets into the capital.
On Thursday, government air strikes in Douma hit a market and a hospital, killing at least nine people, according to the Observatory.
In August, 117 people were killed in a single day of air strikes in Douma, causing a global outcry.
Throughout Syria's brutal war, both the government and opposition forces have been criticised by rights groups for indiscriminate fire on civilian areas.
More than 250,000 people have been killed since the conflict began in March 2011.