A U.S. Marine has been cleared of criminal wrongdoing in last year's fatal shooting of a relative of Iraq's ambassador to the United States, a U.S. official said Wednesday.

The 21-year-old engineering student, Mohammed Sumaidaie, was killed during a search of his family's home near Haditha on June 25, 2005. U.S. authorities ordered an investigation after Samir Sumaidaie complained that his unarmed cousin had been shot in cold blood.

However, Maj. Douglas Powell, a U.S. military spokesman, said the Naval Criminal Investigative Service determined that the Marine "acted properly in self defense in response to unexpectedly encountering a man pointing an AK-47 at him."

He said in an e-mail that investigators interviewed more than 40 people and conducted forensic examinations of the Marine's weapon. He did not say when the investigation was completed.

"This was an unfortunate incident resulting in a tragic loss of life," Powell said without providing further details.

At the time of the shooting, Samir Sumaidaie was Iraq's ambassador to the United Nations. He has since been appointed the country's envoy to Washington.

Iraqi anger over abuse cases involving American troops have increased since five soldiers and one ex-soldier were accused in the alleged rape-murder of a teenager last March near Mahmoudiya. Her parents and sister were also slain.

Five soldiers from the 101st Airborne Division are accused of raping and murdering Abeer al-Janabi and a sixth is accused of failing to report the crime.

The attack was the latest in a string of allegations that U.S. soldiers and Marines in Iraq have killed civilians, including the alleged massacre of dozens in Haditha last November.