US officials are conducting at least six separate investigations of alleged mistreatment of Iraqi detainees at a prison in Baghdad amid indications that abuse of detainees, including humiliating treatment and beatings, may have occurred at other US facilities.

An official told The Associated Press on Monday that seven US soldiers had been reprimanded in the alleged abuse of Iraqi detainees atthe notoriousAbu Ghraib prison in Baghdad. Six other US military police face criminal charges.

An investigation was continuing at Abu Ghraib, which came to attention last week when CBS's "60 Minutes II" broadcast images allegedly showing Iraqis stripped naked, hooded and being tormented by their US captors.

But officials told NBC News that at least five other investigations were under way to determine

whether similar mistreatment was taking place at other US facilities and could be a symptom of a larger systemic problem.

In an interview with NBC News, a former Iraqi prisoner at a separate detention centre said he was held down by six US soldiers, who he said beat the bottoms of his feet with steel rods.

The former prisoner, who spoke only on condition that he not be identified, said that he had cheered the ouster of former Iraqi President Saddam Hussein but that after his treatment at the hands of his US captors, he considered the Americans to be as bad as "10 Saddams."

Lawrence Di Rita, a spokesman for the Defence Department, acknowledged that five military investigations had been launched as a result of the Abu Ghraib cases. The nature of the sixth investigation could not immediately be determined.

Publicly, the Defence Department blamed the commander of the 800th Military Police Brigade, Reserve Brig. Gen. Janis Karpinski, for a breakdown in command at Abu Ghraib, slapping her with an "admonishment" after she left Iraq earlier this year as part of a rotation of US forces.

But US officials noted that Karpinski - who was not suspended or relieved of her command, her lawyer, Neal Puckett, said on ABC's "Good Morning America" - oversaw 25 other detention centres in addition to Abu Ghraib.

A confidential Army report obtained Monday by NBC News found that at least some irregularities in the treatment of Iraqi prisoners extended beyond Abu Ghraib, noting that "the various detention facilities operated by the 800th MP Brigade have routinely held persons brought to them by Other Government Agencies (OGAs) without accounting for them, knowing their identities, or even the reason for their detention."

Military intelligence officers and civilian interrogators encouraged soldiers to abuse prisoners to "soften them up" for interrogation,

the report said, adding, "This systemic and illegal abuse of detainees was intentionally perpetrated." It said its conclusions were supported by written confessions by some of the suspects, among other evidence.

The official said he believed that the investigations of the officers were complete and that they would not face further action or court-martial. However, the reprimands could spell the end of theircareers.

Prisoners told US investigators that their military guards beat them with broom handles and chairs, threatened to rape male prisoners, and sodomised them with chemical light sticks and broom handles.