A videotape surfaced on the Internet Tuesday showing what was said to be the confession and beheading of an Arab Shiite Muslim, presumably Iraqi, whom the insurgents accused of working with the U.S. military.

The video's authenticity could not be verified, but it was posted in the name of the Ansar al-Sunnah Army (search), on a Web site where such militant content is often released. It showed a man, who identified himself as Al-Sayed Alaa al-Malki, kneeling in front of two masked gunmen.

Two identification cards were hanging from the man's gray shirt. One of them bore the name al-Malki and said "local sheik." It also had a photograph that showed him wearing a black robe and a white turban similar to those worn by Shiite clerics.

The bearded, heavyset man, his face bruised and dark circles under his eyes, spoke in a shaky voice of ties to a Shiite militia and to a former U.S. military commander in Iraq. Then, he was shown held down on his back, his face covered with a white sheet and his head being cut off. Afterward, the sheet was removed to show his face.

The death was part of an upsurge in decapitations of both foreigners and Iraqis that have swept Iraq since last spring.

Insurgents in Iraq have kidnapped more than 150 foreigners in their campaign to drive out coalition forces and hamper reconstruction. Many Iraqis also have been killed on suspicion of cooperating with U.S.-led forces in Iraq, but Internet videos of beheadings generally have been of foreigners abducted to pressure foreign governments or companies to stop doing business with the Americans.

In the video posted Tuesday, the man, whose accent was Iraqi, said he was a follower of Iraqi Shiite cleric Muqtada al-Sadr (search). He said he "had close relationship with the Sadr army ... and relations with political leaders such as the (Lt. Gen. Ricardo) Sanchez."

Sanchez was replaced as head of U.S. and coalition forces in Iraq on July 1 by Gen. George Casey. He remains commander of the Army's V corps, based in Germany.

In Baghdad, an al-Sadr aide, Abdul Hadi al-Daraji, told The Associated Press he couldn't immediately verify that the cleric belonged to al-Sadr's camp.

"I have not heard of him before, but I am contacting other al-Sadr followers," he said.

Al-Daraji condemned those who carry out beheadings, regardless of al-Malki's affiliation.

"These people do not serve Islam. They blemish the reputation of Islam," he said. "This is proof that they do not represent resistance to occupation, but rather aim at inciting strife."

The video showed the man saying he worked with an American military officer named Paul, with whom he allegedly established a "Citizens Claims Office" that was used as a cover "to collect and buy weapons from the street, and sell them to the American army."

A statement purportedly from the Ansar al-Sunnah Army that accompanied the video said al-Malki was killed because "he used the Citizens Claims Office as an underground tunnel — during his work with the American forces — to assassinate a number of Sunni leaders."

Shiites make up some 60 percent of Iraq's 25 million people but were marginalized and often brutalized under former dictator Saddam Hussein, who is a Sunni Muslim.

The statement was more of a message showing the group's antagonism toward the Shiite religious sect; the same message was conveyed in an audio tape posted on another Islamic Web site in July by the spiritual adviser of Tawhid and Jihad (search), Abu Anas al-Shami. In the audio, he attacked Shiites, cursed and accused them of attacks on Sunnis and said they are allied with the U.S.-led forces.

A 17-page letter allegedly written by Tawhid and Jihad leader Abu Musab al-Zarqawi (search) appealed to Al Qaeda leaders to help spark a civil war between the two sects in Iraq.