Chilling footage has emerged on YouTube showing a pro-Morsi supporter shot by snipers believed to be riot police as he tries to help another wounded man outside Rabaa mosque in Cairo.

The one-minute video portrays five people attempting to lift another man, who has blood stains on his back and appears to be severely wounded. As the debris and shattered tents show, the clip seems to have been taken outside the camp that was stormed by security forces at the start of the murderous crackdown against pro-Morsi protesters there.

After a few abortive attempts, a man in pink shirt manages to get the wounded man on to his shoulders and starts to run for cover. But he is shot in the back and crumbles to the ground along with the wounded man.

Although his assailant has not been pictured, protesters have claimed that the bullet was fired by riot police.

The video surfaced after the interior ministry announced that it had instructed police to use live ammunition in dealing with attacks on government buildings and police officers.

Earlier, US president Barack Obama cancelled the biannual Bright Star joint military exercise with Egypt in the first concrete action against the military-backed regime's murderous crackdown on pro-Morsi supporters.

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