Syrian army shelling and helicopter attacks on suburbs of the capital Damascus killed at least 62 people on Monday, Opposition activists said.
Eleven of the dead were killed in the district of Jobar, where activists said a Syrian helicopter was downed earlier in the day, they said.
Five of the Jobar victims were captured in Dayer Jdayeh Street and summarily executed by security forces, and the others died when their homes were hit, opposition activists said.
Syrian authorities have banned entry to most foreign media, making it impossible to verify accounts by activists and residents.
Fighting in Damascus between the army and rebels fighting to topple President Bashar al-Assad has grown increasingly violent in recent months.
Assad's seat of power, once seen as immune to the violence, has now become a focus of the 17-month conflict.
"Shells hit a row of flats. We pulled out four bodies from inside, including a child," said one resident of Jobar, who did not want to be named for fear of reprisals.
Rebels have intensified guerrilla attacks on Assad's forces in the capital. The army has responded with artillery, mortar and aerial bombardment, as well as arrest raids.
"It appears that eastern Damascus is being subjected to collective punishment," Yasmine, one of the activists, said from the capital.
"The shelling and helicopter fire are directly targeting civilians in their homes."
Footage released by opposition campaigners showed 20 bodies on the floor of a mosque in the adjacent neighbourhood of Zamalka, including three children.
"I pray that you (Assad) will see your own children like this," said one man, gently moving the head of a dead boy whose jaw appeared to have been sliced through by shrapnel.
In a statement, the Zamalka Coordination Committee activist group said: "The humanitarian situation in horrific. Dead and wounded people are in the streets and cannot be reached because of the ferocity of the bombardment."
Activists said the rest of the casualties were reported killed in helicopter and mortar shell bombardment on the suburbs of Irbin, Harasta, Kfar Batna and Muleiha, on the eastern outskirts of the capital.
Video footage from the Damascus suburb of Harasta showed what appeared to be a mortar round falling on a street lined with shops, with the cameraman yelling: "God is greatest", as parked cars around him burst into flames.