US military investigators in Iraq went into overdrive today to discover who took a picture of Saddam Hussein in his Y-fronts, a picture that they claimed could be in breach of the Geneva Convention.

The photograph appeared on the front pages of The Sun and the New York Post this morning, variously headlined "Tyrant's In His Pants" and "Butcher of Sagdad".

Its subject was easy to recognise, even without his clothes: Hussein, the former Iraqi president, has been in the hands of the US-led coalition in Iraq since he was flushed out of his bolthole near Tikrit in December 2003.

Journalistically, it was a great scoop. The picture, grainy and probably snatched on a mobile phone, is the first to appear of Saddam since a 26-minute court appearance last July.

A second picture of the deposed dictator washing his own trousers in jail displaced The Sun's traditional Page 3 model and a third showed him sleeping in his cell.

But the US military in Iraq was not amused and announced that the lapse was being "aggressively investigated". The photos, it said, "were taken in clear violation of Department of Defence directives and possibly Geneva Convention guidelines for the humane treatment of detained individuals".

That the subject of the pictures is awaiting trial for alleged crimes against humanity is beside the point, legally. Article 13 of the Third Geneva Convention of 1929 is clear enough: "Prisoners of war must at all times be protected, particularly against acts of violence or intimidation and against insults and public curiosity."

Although there is some ambiguity about Saddam's exact status, he was recognised as a prisoner of war after his arrest on the grounds that he had been commander-in-chief of the Iraqi armed forces.

Legal experts say that as long as he remains in US military detention - even if he has now been charged under the Iraqi legal system - then he should retain that status.

The International Committee of the Red Cross (ICRC), which monitors the application of the Conventions and whose representatives have visited Saddam at his top-secret jail, did not appear today to share the American concerns about whether the photographs represented a breach of the rules of war.

Although the ICRC makes every effort to mask the identity and location of PoWs in its own publications, a spokesman for the Geneva-based organisation said today that it was not planning any public statement about the picture of Saddam in his underpants.

"There's only a breach if the detaining authority publish the pictures," said ICRC spokesman Ian Piper. "It's not a breach if they were leaked against the wishes of the detaining power, which I believe to be the case."

He added: "If it's correct that the Americans are unhappy and are pursuing it, that's just how it ought to be. We won't be making any public statements about it."

Saddam's defence lawyer in Baghdad, Khalil al-Duleimi, was under no doubt that the pictures did violate his client's human rights - and who was to blame.

"I don’t doubt such behavior from the American forces because they don’t respect the law. They impose the law of force and the law of the jungle," Mr al-Duleimi said. "They don’t respect human rights and I expect them to do anything."

He added that "if these photographs are authentic, then they represent a clear and blatant violation of all moral and human rights principles. They are a flagrant violation of the Geneva Conventions concerning prisoners of war and my client is a war prisoner."

One problem for American military investigators is that if they do decide that there has been a breach of the Geneva Conventions, then they might then have to look at why US officials decided to parade Saddam after his capture on December 13, 2003.

The US-released video footage of Saddam with matted hair and dirty beard, having his mouth examined by a military doctor, was possibly more humiliating than those grainy photographs published today.

Matthew Happold, an expert in international law at Nottingham University, said today that he regarded publication of the photos as a "technical breach" of the Geneva Conventions that fell far short of a war crime.

"From a common-sensical, non-legal view, it doesn't sound so serious to me. It's probably a guard who has taken pictures on his mobile phone," Mr Happold said.

"The interesting thing is when are they going to get round to putting him on trial and I get the suspciion that no one's too keen on doing it."

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