Dozens of tortured bodies have been found in a flashpoint district of Damascus, a watchdog reported on Monday, in one of the worst atrocities in Syria's 21-month conflict.
The report from the Syrian Observatory for Human Rights came as a gruesome video emerged on the Internet of a separate slaying of three children who had their throats slashed, also in the capital.
"Thirty bodies were found in the Barzeh district. They bore signs of torture and have so far not been identified," said the Britain-based Observatory.
The Syrian Revolution General Commission, a grassroots network of anti-regime activists, estimated there were 50 bodies, and added that "their heads were cut and disfigured to the point that it was no longer possible to identify" them.
The video posted online by activists showed the bodies of three young boys with their throats slit open and hands bound behind their backs. Their bodies were discovered on Monday in Jubar.
The Observatory also reported the killing of the boys, who opposition activists said had been kidnapped the day before at a checkpoint on their way home from school.
These reports could not be verified independently because of media restrictions by the Syrian authorities.
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Regime warplanes, meanwhile, bombarded rebel positions on the northeastern and southwestern outskirts of Damascus, leaving eight civilians dead including two children, said the Observatory.
Southwest of the capital, fierce fighting erupted in the town of Moadamiyet al-Sham with 11 rebels killed in clashes and a child killed in shelling.
In neighbouring Daraya, rebels destroyed a tank as army reinforcements massed in the battleground town, where more than 500 people were reportedly killed in the conflict's bloodiest massacre in August.
Eight civilians, four of them children, were killed in shelling in the Marjeh district of Syria's second city Aleppo, where fighting has been at a stalemate for months since rebels launched an attack on the commercial hub in mid-July.
Syrian television reported the army was "clearing Aleppo of terrorists".
In the northwestern province of Idlib, fighters from the jihadist Al-Nusra Front and other rebels pressed an offensive on a military post that they stormed two days ago, and continued to lay siege to the nearby Wadi Deif base.
Regime warplanes responded by raiding rebel positions around Wadi Deif, one of the government's last outposts in the largely rebel-held north, as similar raids were made in Daraa province in the south and Deir Ezzor in the east, the Observatory said.
In central Syria, the army shelled the town of Halfaya in Hama province, where an air strike on a bakery last week killed 60 people, and Houla in Homs province, where pro-regime militiamen are suspected of killing more than 100 people in May in another major massacre.
The Observatory, which relies on medics and activists on the ground in compiling its tolls, gave an initial toll of 59 people killed on Monday.