Dozens of bloodied bodies have been buried in mass graves in a Damascus suburb where activists claim more than 300 people have been killed over the past week in a major government offensive to take back control of rebel-held areas in and around the capital.
The British-based activist group Syrian Observatory for Human Rights said 32 more dead bodies were found in the streets of Daraya on Sunday and that they had been killed by "gunfire and summary executions".
Among them were three women and two children, the group said. It put the toll for the past week as at least 320.
Another activist group, the Local Coordination Committees, claimed 300 bodies were discovered on Saturday in Daraya and 633 people have been killed there since the government launched its assault last week.
President Bashar Assad, in comments carried by state media, reiterated his long-standing claim that a foreign plot was behind the uprising against his rule and said he would not allow it to succeed "whatever the price might be".
Britain's minister for Middle East affairs, Alistair Burt, meanwhile, said if confirmed, the massacre "would be an atrocity on a new scale requiring unequivocal condemnation from the entire international community".
He added that it "highlights the urgent need for international action to bring an end to the violence, end this culture of impunity and hold to account those responsible for these terrible acts".
Mr Burt said he had discussed the killings with UN and Arab League joint special representative for Syria Lakhdar Brahimi.
It was impossible to independently verify the death tolls because of severe restrictions on media coverage of the conflict. But activists and residents have reported excessive use of force by the regime in major battles, with indiscriminate shelling from the ground and the air.
The Local Coordination Committees said some of those killed by regime forces in Daraya were buried in mass graves today. Video footage posted by the group showed bloodied bodies wrapped in colourful blankets lying next to each other with branches of date palms strewn over them. Another video posted on the internet and dated yesterday showed dozens of bodies on the floor of a mosque in Daraya. Most of the bodies were bloodied and wrapped in blankets.