The US military started an investigation on Friday into the publication of photos showing former Iraqi leader Saddam Hussein in underwear when he was in US military detention, US officials said.

The photos of the former Iraqi president, who was toppled in April 2003 and captured by the US military in December that year, were published on Friday in The Sun, a London-based newspaper, and The New York Post.

One picture showed Saddam Hussein wearing only a pair of white briefs and holding a pair of trousers in his hand.

The publication of the photos might be meant to deal a blow to the resistance in Iraq, an article in the Sun newspaper quoted US military sources as saying.

The release of the photos, which were believed to have been taken over a year ago, was unauthorized, said Bryan Whitman, a Pentagon spokesman.

"This is clearly something we wouldn't condone, or would sanction, and it is troubling that images like this could make their way to the public when they shouldn't," he said.

US President George W. Bush and Defense Secretary Donald Rumsfeld were informed of the investigation, officials said.

White House spokesman Trent Duffy said Bush "strongly supports the aggressive and thorough investigation that is already under way."

He said the source of these photos was unknown at this time, and the photos "are in clear violation of DOD (Department of Defense) directives and possibly Geneva Convention guidelines for the human treatment of detained individuals."

Duffy said the president and the US-led multinational forces in Iraq "are very disappointed at the possibility that someone responsible for the security, welfare and detention of Saddam Hussein would take and provide these photos for public release."

Bush said the photos were unlikely to inflame the insurgency in Iraq. "I don't think a photo inspires murderers. I think they are inspired by an ideology that is so barbaric and backwards that it is hard for many in the western world to comprehend how they think," Bush said.