An Iraqi insurgent group which has claimed responsibility for the downing this week of a U.S. helicopter in central Baghdad that killed five Americans, posted on Thursday a video tape on an Islamic Web site showing footage of the helicopter wreckage and two bodies.

The one-minute-14-seconds long video carried the logo of the 1920 Revolution Brigades, a known Sunni militant group. It showed wreckage of a helicopter with bricks scattered around it. The bodies of two men, their torsos naked, one with gray hair and the other dark haired, were seen lying next to one another beside the wreckage.

"Our heroes were able to shoot the film of the helicopter wreckage after they downed it over a roof of a house of a citizen," said the insurgent group's statement.

Click here to see the footage (WARNING: GRAPHIC CONTENT).

Earlier Thursday, Iraqi and U.S. officials said that four of the five Americans who died in the downing of a U.S. security company's helicopter in a dangerous Sunni neighborhood in central Baghdad on Tuesday were killed on the ground, execution style, in the back of the head.

But the two bodies shown in the footage had no visible gunshot wounds to the head or any other visible wounds .

Another militant group, Ansar al-Sunnah Army, which has also claimed responsibility for the downing of the helicopter, said in a statement posted Wednesday on an Islamic Web site that its fighters "rushed toward the crash of the helicopter while under fire from a second (U.S.) helicopter and killed three U.S. soldiers."

The authenticity of the two statements could not be verified.

The helicopter, owned by Blackwater USA, was shot down after racing to help a U.S. Embassy ground convoy that had come under fire in the Sunni neighborhood. A second helicopter also was hit but there were no casualties among its crew, a Washington official said.

The Ansar al-Sunnah Army posted with its statement an ID card it claimed was of a man who was on the helicopter. The card bore the name of Arthur Laguna, later identified by his mother as among those killed. Laguna was a 52-year-old pilot for Blackwater, which provides security for State Department officials in Iraq, trains military units from around the world, and works for corporate clients.

The crash of Blackwater's small surveillance helicopter was the second in a week associated with the U.S. war effort in Iraq.

A U.S. Army Black Hawk helicopter went down Saturday northeast of Baghdad, killing all 12 service members on board, including two colonels, one lieutenant colonel and two command sergeants major. It was the largest number of key officers and sergeants killed in a single incident since the Iraq war started nearly four years ago.

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