WASHINGTON, Sept 10: As many as 100 "ghost detainees", many more than originally revealed, were held secretly by US forces in Iraq, the army general leading an Abu Ghraib prison abuse probe told a congressional committee Thursday.

General Paul Kern told members of the Senate Armed Services Committee that investigators had "found many reports ... of people that were brought into the facilities and who were moved so that they could not be identified by the International Red Cross.

"This is in violation of our policy, which requires us to register people so that it can be reported that they are being held in detention," he said. Kern said the Pentagon has commissioned two probes - by the Department of Defence Inspector General and the CIA Inspector General - into the illegal practice, which he described as "perhaps one of the more troubling pieces of our investigation".

As recently as several weeks ago, the team of investigators had estimated that US forces hid just eight ghost detainees from the International Committee of the Red Cross in violation of the Geneva Convention.

While Gen Kern said officials now believe that perhaps as many as 100 secret detainees had been held, another Pentagon investigator, Major General George Fay, said he believed the number to be somewhat lower, "maybe two dozen or so - maybe more".

Gen Kern and Gen Fay said the Pentagon was seeking more concrete figures from the Central Intelligence Agency, which played a key role in many of the interrogation at the prison, to determine exactly how many inmates were secretly held.

Gen Kern made his remarks as the Armed Services Committee heard testimony into failures of oversight that allowed the scandal to occur. The non-profit group Human Rights Watch denounced the hidden imprisonment.

"Secret detention is the gateway to torture," Reed Brody, legal counsel for the New York-based organization, said in a statement. "History shows that when people are taken off the books, that is when they are most vulnerable to all kinds of abuse, including mistreatment, torture and even disappearance."

The chairman of the Senate committee, Republican John Warner of Virginia, said at the hearing that more than 300 allegations of abuse of prisoners in Iraq and Afghanistan have been made to date, and that 66 allegations of abuse have been substantiated at Abu Ghraib.

The prison abuse scandal became a cause celebre in April, after several now-notorious photographs depicting the abuse at Abu Ghraib were published around the world. Gen Kern restated the finding of the Pentagon's probe released in a detailed report last month, that the primary cause of detainee abuse was "individual misconduct".

But he also again cited "a failure of leadership and a failure of discipline" up the military chain of command. Pentagon officials testified that they have drawn lessons from the Abu Ghraib scandal, and have put in place far-reaching reforms since the revelations of the prison abuse became public.

"I will tell you today that if you visited Abu Ghraib, if you visited with our soldiers, you would see a very, very different picture," said Gen Kern, who said that the prison population has been reduced from 7,000 to 2,400.

Many detainees have been freed, he said, or turned over to Iraqi authorities. In addition, soldiers now are given extensive training "to know that they clearly understand the rules of interrogation and detention," he said.

In a separate hearing later on Thursday, former Defence Secretary James Schlesinger, who led an independent probe into the prison abuses, noted that virtually all of the mistreated inmates seen in the widely publicized abuse photos were non-combatants who were of no intelligence value.

"Most of those photographs that you saw involved criminals," Mr Schlesinger said. He was asked by Senator Joseph Lieberman about the prison guards' motivation for the abuse.

"If it was not to get intelligence, relevant information, out of the detainees, why were the dogs put on them?" Senator Lieberman asked. "Why were they held on leashes? Why were they asked to strip?" "In some cases," Mr Schlesinger replied, "just pure sadism." -AFP