Washington ? Military investigators probing the deaths in November of about two dozen Iraqi civilians have evidence that points toward unprovoked murders by Marines, a senior defense official said Friday.

The Marine Corps initially reported 15 deaths and said they were caused by a roadside bomb and an ensuing firefight with insurgents. A separate investigation is aimed at determining if Marines lied to cover up the events, which included the deaths of women and children.

If confirmed as unjustified killings, the episode could be the most serious case of criminal misconduct by U.S. troops during three years of combat in Iraq. Until now the most infamous occurrence was the Abu Ghraib prisoner abuse involving Army soldiers, which came to light in April 2004 and which President Bush said Thursday he considered to be the worst U.S. mistake of the war.

The defense official discussed the matter Friday only on condition of anonymity because he was not authorized to talk publicly about the investigation. He said the evidence found thus far strongly indicated the killings in the insurgent-plagued city of Haditha in the western province of Anbar were unjustified. He cautioned that the probe was not finished.

The mother of Police Capt. Salam Monati Yussef, who was shot and killed Thursday, grieves at her son's funeral Friday in Kirkuk, Iraq. Incidents Friday proved that sectarian violence is still on the rise in Iraq: A bomb exploded in an outdoor market in a majority Shiite part of east Baghdad, and Sunni leaders closed mosques in Basra to protest a drive-by shooting.

Once the investigation is completed, perhaps in June, it will be up to a senior Marine commander in Iraq to decide whether to press charges of murder or other violations of the Uniform Code of Military Justice.

Three officers from the unit involved – 3rd Battalion, 1st Marine Regiment, 1st Marine Division, based at Camp Pendleton, Calif. – have been relieved of duty, although officials have not explicitly linked them to the criminal investigation.

In an indication of how concerned the Marines are about the implications of the Haditha case, their top officer, Gen. Michael Hagee, flew Thursday to Iraq. He was to reinforce what the military said was a need to adhere to Marine values and standards of behavior and to avoid the use of excess force.