Syrian forces and militiamen loyal to President Bashar al-Assad killed at least 85 people, including women and children, when they stormed a Damascus suburb after five days of fighting.
Opposition activists today described the attack in Jdeidet al-Fadel as a 'massacre', although there has been no official confirmation of the assault.
Syrian authorities have banned most independent media from the country since the uprising began two years ago.
Horror: Countless civilians have been caught up in the fighting, which has resulted in at least 70,000 deaths
Conflict: Syrian rebel fighters inside a ruined mosque in Aleppo this week, the scene of fierce fighting
Jamal al-Golani, a member of the Revolution Leadership Council opposition group, said the number of dead may be higher than 250.
More...
Was Boston bomber inspired by Russia's Bin Laden? Mother claims FBI tracked older brother 'for FIVE YEARS' after being told by Moscow of links to Chechen terrorists
Britain's secret role in America's drone war: Government approves UK defence company to supply technology to the U.S.
The lost Briton of Guantanamo: He's been cleared - but had a devastating secret about MI6 and the Iraq invasion which means he can never be freed
Death toll: Syrian forces and militiamen loyal to President Bashar al-Assad (pictured) killed at least 85 people after fierce fighting in a Damascus suburb
He said most of those killed were shot at close range, but the presence of army patrols has made documenting the deaths difficult.
The killings happened over several days as and after pro-Assad forces stormed an area where there were up to 270 rebels, Golani said.
He added that he had counted 98 bodies in the streets and 86 people who he said had been summarily executed in makeshift clinics where they were lying wounded.
Abu Ahmad al-Rabi, an activist in the adjacent district of Jdeidet Artouz, said: 'We documented 85 summarily executed, including 28 shot in a makeshift hospital after Assad's forces entered Jdeidet al-Fadel. We fear that the victims of the massacre are much higher.'
According to the BBC, Syria's state news agency, Sana, said government forces had 'inflicted heavy losses upon terrorist' in the suburb.
The UK-based Syrian Observatory for Human Rights has put the death toll at least 80, many of whom were killed either by execution or shelling.
Opposition fighters had reportedly pulled out of the town yesterday after running out of ammunition, and government forces had taken full control of the area by this morning.
There have also been reports of fighting in the Sunni areas of the largely Christian town of Jdeydet Artuz,close by, and in the rebel held Daraya.
The army has been accused of staging a 'fierce attack' in areas south and west of the capital by the Syrian Nation Council opposition, according to Al Jazeera.
Loyal: Members of the Damascus Youth volunteer group visiting army checkpoints in Damascus this week
Troops: Syrian Army soldiers showing off their skills to mark the country's Independence Day on Wednesday
It had said yesterday that Jdeydet al-Fadel and other areas were 'subjected to a siege' and had been 'deprived of all basic needs for human life'.
At least 70,000 people have been killed in the country since fighting began two years ago.
US Secretary of State, John Kerry, announced yesterday the U.S. was doubling the aid it gives to the country's rebels, including non-lethal military equipment.
Rebels have insisted that any weapons they receive would not fall into the 'wrong hands', amid fears by the U.S. and Britain that they could end up with Islamist extremists.