President Bush promised on Wednesday that any Marines involved in the alleged murders of Iraqi civilians will be punished. A senior officer said the case could undermine Iraqis' support for the presence of American troops.

U.S. President George W. Bush walks from the Marine One helicopter upon his return to the White House in Washington after attending a Republican party fundraiser for U.S. Congressional candidates in Baltimore county, MD May 31, 2006. [Reuters]

"I am troubled by the initial news stories," Bush said in his first public comments about the deaths of about two dozen civilians at Haditha last November. "I'm mindful that there's a thorough investigation going on. If in fact, laws were broken, there will be punishment."

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

The shootings came after a bomb rocked a military convoy on Nov. 19, killing a Marine. Residents of Haditha said Marines then went into nearby houses and shot members of two families, including a 3-year-old girl.

At first, the American military described what happened as an ambush on a joint U.S.-Iraqi patrol, with a roadside bombing and subsequent firefight killing 15 civilians, eight insurgents and a Marine. The statement said the 15 civilians were killed by the blast, a claim the residents strongly denied.

With some in Congress alleging a cover-up, the Bush administration offered assurances the facts will be made public.

Bush's spokesman, Tony Snow, urged patience as the Marines conduct what he called a vigorous investigation. He said a report will come out in "a matter of weeks, not a matter of months" and include public release of photographic evidence. "We're going to see everything," Snow said.

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

At the Pentagon, Army Brig. Gen. Carter Ham would not discuss any aspect of the probe, but he stressed the potential harm caused by allegations alone.

"Allegations such as this, regardless of how they are borne out by the facts, can have an effect on the ability of U.S. forces to continue to operate," said Ham, a deputy operations director for the Joint Staff and a former commander of U.S. forces in northern Iraq.

"We do rely very heavily and more importantly, the Iraqi security forces rely heavily on the support from the Iraqi people," Ham said. "And anything that tends to diminish that, obviously, is not helpful to what we're trying to do."

The toll of Iraqi civilians climbed on Wednesday when two women, including one being taken to a maternity hospital, died when coalition troops shot at a car that failed to stop at an observation post in a city north of Baghdad. The U.S. military said the vehicle entered a clearly marked prohibited area but failed to obey repeated warnings.

The president was asked about the Haditha allegations during a photo opportunity with the president of Rwanda, Paul Kagame.

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."

Until now the most infamous violation of military law in Iraq was the Abu Ghraib prisoner abuse involving Army soldiers, which came to light in April 2004. Bush said last week he considered Abu Ghraib to be the most costly U.S. mistake of the war.