An internal investigation by the US Army exposed "sadistic, blatant and wanton criminal abuses" of Iraqi prisoners, according to The Times.

The revelation, which is set to inflame Arab sentiments, came as American officials admitted on Tuesday that US troops murdered two Iraqi prisoners at Abu Ghraib prison.

Democratic senator Edward Kennedy, emerging from a briefing with military officials, said the abuse at Abu Ghraib did not appear to be an isolated incident, according to The Times.

He said there were reports of further mistreatment in Iraq and Afghanistan.

The military has convicted one US soldier of killing a prisoner by hitting him with a rock, The Times quoted officials as saying. He was reduced in rank to private and thrown out of service, but did not serve any time in jail. A private contractor working for the Central Intelligence Agency was also found to have killed a prisoner.

There have been 35 criminal investigations into claims of prisoner abuse and deaths in Iraq and Afghanistan since December 2002, military officials said.

The internal report, marked 'Secret, no foreign dissemination', but seen by The Times, details at least 20 ways in which US guards abused detainees at Abu Ghraib.

The inquiry, led by Major General Antonio Taguba, was started in January and reported in March.

The general concluded that the abuse was "systemic and illegal", and "intentionally perpetrated" by officers from the 800th Military Police Brigade.

The abuse, included: breaking chemical lights and pouring the phosphoric liquid on detainees; threatening detainees with a charged 9mm pistol; beating detainees with a broom handle and a chair; threatening male detainees with rape; sodomising a detainee with a chemical light and perhaps a broom stick; using military working dogs to frighten and intimidate detainees with threats of attack, and in one instance actually biting a detainee.

Detainees were also forcibly arranged in sexually explicit positions and photographed, stripped and kept naked for several days at a time, forcing to wear women's underwear and forced to masturbate while being photographed and videotaped.

Gen Taguba said he found the charges "credible, based on the clarity of their statements and supporting evidence provided by other witnesses".

Defence Secretary Donald Rumsfeld said the Pentagon would do everything to bring to justice "those that may have violated the code of military conduct and betrayed the trust placed in them by the American people".