Updated

President Bush said Wednesday he was troubled by allegations that U.S. Marines had killed unarmed Iraqi civilians and that, "If in fact laws were broken, there will be punishment."

It was Bush's first public comment on allegations that Marines killed about two dozen unarmed Iraqis in the western city of Haditha last November.

Bush said he had discussed Haditha with Gen. Peter Pace, chairman of the Joint Chiefs of Staff. "He's a proud Marine. And nobody is more concerned about these allegations than the Marine Corps. The Marine Corps is full of honorable people who understand the rules of war."

"If in fact these allegations are true," Bush said, "the Marine Corps will work hard to make sure that that culture — that proud culture — will be reinforced. And that those who violated the law, if they did, will be punished."

The president was asked about the Iraq allegations during an Oval Office photo opportunity with the president of Rwanda, Paul Kagame.

"I am troubled by the initial news stories," Bush said. "I'm mindful that there's a thorough investigation going on. If in fact, laws were broken, there will be punishment."

The killings at Haditha, a city that has been plagued by insurgents, came after a bomb rocked a military convoy on Nov. 19, killing a Marine. Rep. John Murtha, a Pennsylvania Democrat and decorated war veteran who has been briefed by military officials, has said Marines shot and killed unarmed civilians in a taxi at the scene and went into two homes and shot others.

Military investigators have evidence that points toward unprovoked murders by Marines, a senior defense official said last week.

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 Bush said he considered to be the worst U.S. mistake of the entire war.

Once the military 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.

White House press secretary Tony Snow said Wednesday there is no firm date for release of the investigative report. But he said he suspects it will come out in "a matter of weeks, not a matter of months" and include photographic evidence.