A video which appears to show a Syrian rebel taking a bite from the heart of a dead soldier has been widely condemned.
US-based Human Rights Watch identified the rebel as Abu Sakkar, a well-known insurgent from the city of Homs, and said his actions were a war crime.
The main Syrian opposition coalition said he would be put on trial.
The video, which cannot be independently authenticated, seems to show him cutting out the heart.
"I swear to God we will eat your hearts and your livers, you soldiers of Bashar the dog," the man says referring to President Bashar al-Assad as he stands over the soldier's corpse.
Human Rights Watch (HRW) says Abu Sakkar is the leader of a group called the Independent Omar al-Farouq Brigade.
"The mutilation of the bodies of enemies is a war crime. But the even more serious issue is the very rapid descent into sectarian rhetoric and violence," HRW's Peter Bouckaert told Reuters news agency.
HRW said those committing war crimes on either side had to know that there was no impunity and that they would be brought to account.
The human rights group said Abu Sakkar had been filmed before, firing rockets into Shia areas of Lebanon and posing with the bodies of guerrillas from the Lebanese Hezbollah movement killed fighting alongside Syrian government forces.
The video, posted on Sunday, is one of the most gruesome to emerge among the many thrown up by more than two years of carnage in Syria, says the BBC's Jim Muir in Beirut.