Iraq's U.N. ambassador accused U.S. Marines of killing his unarmed young cousin in what appeared to be "cold blood" and demanded an investigation and punishment for the perpetrators.

In an e-mail to friends obtained Friday by The Associated Press, Ambassador Samir Sumaidaie (search) said the killing took place in his ancestral village in western Anbar province, where U.S.-led forces have been conducting a counterinsurgency sweep aimed at disrupting the flow of foreign militants into Iraq (search).

His cousin Mohammed Al-Sumaidaie (search), 21, a university student, was killed June 25 when he took Marines doing house-to-house searches to a bedroom to show them where a rifle which had no live ammuntion was kept, the ambassador said. When the Marines left, he was found in the bedroom with a bullet in his neck.

Richard Grenell, spokesman for the U.S. Mission, said acting U.S. ambassador Anne Patterson received a call from the Iraqi ambassador "and expressed her heartfelt condolences on this terrible situation, and contacted senior State Department and Pentagon officials to look into the matter immediately."

The U.S. military issued a statement in response late Friday.

"The events described in the allegations roughly correspond to an incident involving Coalition Forces on that day in that general location; therefore a military inquiry has been initiated," the statement said.

"We take these allegations seriously and will thoroughly investigate this incident to determine what happened," the statement quoted Maj. Gen. Stephen T. Johnson as saying. The investigation could take several weeks, the statement said.

Sumaidaie said the killing represents "a betrayal" of the values and aspirations of Iraqis and Americans to defeat the terrorists and build a country based on freedom, democracy, and respect for human rights and the rule of law.

"It is a betrayal of the American people who are making huge sacrifices to bring this about, and a betrayal of Iraq and all Iraqi patriots who have put their trust in the United States," he said.

In the letter, Sumaidaie gave a detailed account of the tragedy.

Mohammed, an engineering student at the University of Techology in Baghdad, was visiting his family in the village of Al-Shaikh Hadid when the Marines knocked on the door, the ambassador said.

The young man rushed to open the door and greeted the group of about 10 Marines and an interpreter who appeared to be Egyptian pleasantly, "happy to exercise some of his English," he said.

The Marines asked if there were any weapons, and Mohammed said there was a rifle, which only had blanks, the letter said. He then led some of the Marines into his father's bedroom where it was kept, Sumaidaie wrote. His father, the local headmaster, was at school.

A short time later, his mother, brothers and sisters who were kept in the living room heard a thud but they were generally relaxed because they had nothing to hide, and "they thought, nothing to fear," he said.

But later a younger brother, Ali, was dragged by the hair into the corridor by a Marine and was beaten. The mother started sobbing. A Marine then went out and returned with a camera and went into the bedroom. After a while, the family went outside and waited on the porch as they were ordered, the ambassador said.

More than an hour later, as the soldiers were leaving, the interpreter asked the mother in Arabic if that was her son inside. When she replied "yes," the interpreter said, "they killed him!," Sumaidaie said.

"The mother let off a deafening cry of anguish, but the Marines were smiling at each other as they were leaving," he said. "In the bedroom, Mohammed was found dead and laying in a clotted pool of his blood. A single bullet had penetrated his neck," the ambassador said.

The ambassador wrote that he believed "a serious crime has been commited — a crime that may be repeated up and down Al-Anbar" and demanded an investigation into what he said appeared to be the "killing of an unarmed innocent civilian — a cold blood murder."