A video that appears to show Syrian rebels killing soldiers who had surrendered probably constitutes a war crime that should be prosecuted, the United Nations human rights office says.
Anti-government rebels killed 28 soldiers on Thursday in attacks on three army checkpoints around Saraqeb, a town on Syria's main north-south highway.
Video footage, which has been widely publicised around the world, showed some of the dead were shot after they surrendered.
In the video rebels berated the soldiers, calling them "Assad's Dogs", before firing round after round into their bodies as they lay on the ground, Reuters reports.
UN rights spokesman Rupert Colville said this may be just the latest in a string of documented summary executions by opposition factions as well as by government forces and groups affiliated with them.
"It will be examined carefully," Mr Colville told a news briefing in Geneva, saying it may be difficult to identify the perpetrators and the location where the footage was recorded.
"But the allegations are that these were soldiers who were no longer combatants. And therefore, at this point it looks very likely that this is a war crime, another one," he said.
More than 32,000 people are estimated to have been killed since protests against President Bashar al-Assad first broke out and then degenerated into full-scale civil war, with his forces using artillery and air strikes.
UN human rights investigators led by Brazilian Paulo Pinheiro have gathered evidence and testimony on atrocities committed by government forces as well as by armed rebels in the 19-month-old conflict.
In their last report in August, the investigators said government forces and allied militia had committed war crimes including the murder and torture of civilians in what appeared to be a state-directed policy.
The team has already drawn up a confidential list of suspects for future prosecution, either by an international tribunal or by a Syrian national court if feasible.