WASHINGTON, Nov 16: US military officials said on Tuesday they are investigating a videotaped incident in a Fallujah mosque, in which pool television pictures show a US Marine shooting and killing an already captive and wounded Iraqi prisoner.

The shooting on Saturday was videotaped by pool correspondent Kevin Sites, who said three other previously wounded prisoners in the mosque apparently were shot again by Marines inside the mosque.

The tape, broadcast in the United States on Monday, shows a squad of Marines finding a room of wounded rebels inside a mosque, which was a former rebel stronghold and was believed by Marines to be the source of heavy enemy fire.

The tape shows a Marine shouting out that one of the wounded is playing "possum." "He's faking he's dead!" says the Marine. A second Marine says, "And he's breathing!" The first Marine then repeats "He's faking he's dead!" and is shown raising his rifle toward a prisoner lying on the floor of the mosque.

News organizations that have shown the video did not show the bullet hitting the man. At that moment, the video is blacked out but the sound of the rifle can be heard. A Marine then says: "He's dead now." US television reports said the rebels were unarmed - left in the mosque by a previous squad of Marines to await medical evacuation. But the second squad did not know that. Commanders had not evacuated the wounded because US troops were still under fire.

The blacked out portion of the videotape is reported to show the bullet striking the man in the upper body, possibly the head. His blood splatters on the wall behind him and his body goes limp. The cameraman was embedded with the unit.

According to US television reports, a different Marine unit came under fire from the mosque on Friday and those Marines stormed the building, killing ten men and wounding five others. The Marines said the fighters in the mosque had been armed with rocket-propelled grenades and AK-47 rifles. The Marines had treated the wounded, left them behind and continued on Friday with their drive to retake the city from rebels.

The Marine shown firing in the mosque is in custody now as authorities investigate whether the shooting was a criminal act, reports said.

In the videotape, gunfire can be heard from inside the mosque, and at its entrance, Marines who were already in the building emerge. They are asked by an approaching Marine lieutenant if there were insurgents inside and if the Marines had shot any of them.

A Marine can be heard responding affirmatively. The lieutenant then asks if they were armed and a fellow Marine shrugs. The tape showed two of the wounded men propped against the wall and bleeding to death. A third wounded man appeared already dead, while a fourth was severely wounded but breathing. The fifth was covered by a blanket but did not appear to have been shot again after the Marines returned. It was the fourth man who was shown being shot.