The deaths would bring the toll from an offensive by President Bashar Assad forces on Daraya, south-west of Damascus, to 149, according to a tally by opposition activists in the capital.
Due to restrictions on non-state media, it was impossible to independently verify the accounts.
The Daraya Coordination Committee activists’ group said in a statement that among those found with shots to the head were eight members of the al-Qassaa family: three children, their father and mother and three other relatives.
Their bodies were found in a residential building near Mussab bin Umeir mosque in Daraya, the group said.
Mohammad Hur, an activist in Daraya, said 36 bodies of young men were found in one building along with several badly wounded people who could not be transferred to hospitals in the area because the army had occupied them. A further 12 bodies were found in the basement of another building, he said.
“We are in the process of identifying the bodies and documenting how they died. Initial evidence shows that they were mostly shot at close range in the face, neck and head, execution style,” Hur said by telephone.
“Female members from at least two families say that soldiers shot their brothers in front of them,” he added.
The Syrian Observatory for Human Rights, which is based in Britain and headed by dissident Rami Abdelrahman, said it had received reports of dozens of bodies found in Daraya, but it had not yet ascertained how they were killed.
Abdelrahman said at least 300 people had been killed by the army’s offensive on Daraya and the nearby suburb of Mouadamiya in recent days.
The army overran Daraya, one of a series of large Sunni Muslim shanty towns that surround Damascus, on Saturday after three days of shelling and rocket and helicopter bombardment that killed 70 people, according to opposition sources and residents who said most of the dead were civilians.
The attack on Daraya was part of an army campaign to regain control of the outskirts of the capital, a mixture of built up areas and farmland where rebels had regrouped and relaunched guerrilla attacks on Assad’s force.