Evidence found by a preliminary U.S. military inquiry reportedly suggests that Marines may have murdered 24 Iraqi civilians in November, contradicting the troops' claim the victims died in a roadside bomb explosion.

Forensic evidence showed the civilians -- including women and children -- had bullet wounds to their heads and chests.

The victims lived in Haditha, in Abbar province, about 200 kilometres northwest of Baghdad.

"The forensics painted a different story than what the Marines had said," an official, who spoke on condition of anonymity, told Reuters Wednesday.

U.S. President George expressed concern over the alleged incident, and said any Marines found to have carried out such an unprovoked attack would not escape justice.

"I am troubled by the initial news stories," Bush told reporters at the White House Wednesday. "I am mindful there is a thorough investigation going on. If in fact laws were broken there will be punishment."

The White House has said it will make public all findings of the investigation into the alleged killings.

"I have been told and was assured earlier today when I called about it that when this comes out, all the details will be made available to the public, so we'll have a picture of what happened," White House spokesman Tony Snow told reporters Tuesday.

Snow said Bush was advised about the Nov. 19 killings earlier this year when a reporter for Time magazine asked the White House about it.

"The president also is allowing the chain of command to do what it's supposed to do over at Department of Defence, which is to complete an investigation,'' he said.

The U.S. is actually conducting two investigations: one into the deadly encounter, and the second into whether it was covered up.

Originally, 15 civilian deaths were attributed to a car bombing and subsequent firefight that left eight insurgents dead.

However, last week Pentagon officials suggested that the investigation supports allegations that the marines carried out an unprovoked massacre.

It is alleged that the marines were upset after one of their own died in a roadside bombing.

Iraqi Prime Minister Nouri al-Maliki broke his silence Tuesday about the incident, telling the British Broadcasting Corp. that civilian deaths are never justified.

"We emphasize that our forces, that multinational forces will respect human rights, the rights of the Iraqi citizen,'' al-Maliki said. "It is not justifiable that a family is killed because someone is fighting terrorists, we have to be more specific and more careful.''

Some U.S. media have compared the Nov. 19 deaths to the 1968 My Lai massacre in Vietnam, when U.S. soldiers ran amok, killing some 500 people.

With a report by CTV's Joy Malbon