WARNING: Although this video has the most graphic content blurred, some readers may still find its contents disturbing.
The video has emerged from the Syrian city of Homs, scene of some of the most bitter fighting in recent months between Syrian armed forces and those rebelling against the country's president, Bashar Al-Assad.
In the video the rebel, identified as Abu Bakkar, a leading rebel military leader in the area, appears to bend over the dead soldier's body and hack away at his chest with a knife. In seconds he pulls out the man's heart and takes a bite out of it.
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Before his revolting act, he says: "I swear to God we will eat your hearts and your livers, you soldiers of Bashar the dog."
The date of the video cannot be immediately verified, but the New York-based Human Rights Watch condemned it.
Peter Bouckaert of Human Rights Watch said that he had seen an unedited copy of the video and that Abu Bakkar's identity had been confirmed by rebel sources in Homs.
"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," said Bouckaert.
Hundreds of thousands of people have been killed in Syria's civil war in which he regime of President Al-Assad is trying to cling on to power in the face of opposition from a variety of rebel groups, some of whom are backed by Western governments.