A rebel brigade in Aleppo admitted responsibility on Monday for the worst mass killings by Syrian opposition forces since the uprising began, even as the United Nations human rights chief accused them of "murder, extra-judicial execution and torture".
A video posted on Youtube showed a line of 20 men dressed in army fatigues sprawled along a pavement, all wearing blindfolds and clearly having had their hands bound behind their back.
The men were apparently lined up and shot, although this was not shown in the footage. The video commentary names a rebel unit called the Salman al-Farisi battalion, said to be from the town of Al-Bab north-east of Aleppo, and says the dead men were members of the Syrian regime's security forces.
The massacre comes despite an agreement by the major opposition brigades that there should be no repeat of the most notorious mass killing, of four members of the so-called Barri militia, captured in Aleppo and publicly gunned down in a school playground in July.
The troops killed in the latest video were said to have been captured in fighting for control of Masaket Hanano in central Aleppo, where rebels claimed to have taken a major army base over the weekend.
A researcher with the human rights group Avaaz, which has been critical of the regime and documented hundreds of its abuses, said rebels were increasingly admitting to executions of captured soldiers and in particular "Shabiha" or militia. "We have been receiving too many reports about the Free Syrian Army executing people in Aleppo," he said. "It is very ugly. The FSA is doing some terrible things there, and many of them are jihadists."
Other activist groups urged caution, saying they had not heard of the battalion, even though it came from a pro-FSA area. "According to our guys on the ground this is the first time they have heard this name," Moussab Azzawi, of the Syrian Network of Human Rights, said. "The FSA as an organisation has denied responsibility."
Navi Pillay, the UN human rights commissioner, said the fighting was leading to abuses on both sides. "The use of heavy weapons by the government and the shelling of populated areas have resulted in high numbers of civilian casualties, mass displacement of civilians inside and outside the country and a devastating humanitarian crisis," she said in Geneva.
"I am equally concerned about violations by anti-government forces, including murder, extra-judicial execution and torture, as well as the recently increased use of improvised explosive devices."
Although the ideological make-up of the Salman al-Farisi battalion is not clear, it was said to have carried out the operation with the Jubhat al-Nusraa, a jihadist group accused of being aligned with al-Qaeda. Quilliam, a London-based group which monitors jihadist activity, said such groups were playing a larger role in the conflict and moving it towards a "new and more radical phase", though it estimated extremists as comprising under 10 per cent of total rebel forces.
