An influential U. S. Congressman and outspoken critic of the war in Iraq says U.S. Marines responding to a roadside bombing last November may have killed innocent Iraqi civilians.

Representative John Murtha said Wednesday military sources have told him a Pentagon probe of the incident in Haditha indicates the American troops barged into a house near the bombing and killed the Iraqis.

The Democratic congressman, from the U.S. state of Pennsylvania, said combat stress related to the death of a fellow Marine in the bombing prompted the alleged killings.

The Marine Corps had originally claimed the bomb and an ensuing firefight had killed the Marine and the Iraqi civilians.

Three officers from the Marine unit have been relieved of duty in connection with the incident. Marine officials say they have no comment pending the outcome of the investigation.