Baghdad, Oct. 20 (Reuters): The highest-ranking US soldier to be court-martialled in Baghdad?s notorious Abu Ghraib jail case today admitted beating and humiliating prisoners, including forcing some to masturbate.

Staff Sergeant Ivan Frederick told the hearing at a military camp on the outskirts of Baghdad he had been trying to prepare the detainees for interrogation. Frederick, 38, pleaded guilty to five charges, including indecent acts and dereliction of duty and assault. ?I was wrong about what I did and I shouldn?t have done it. I knew it was wrong at the time because I knew it was a form of abuse,? Frederick said. The charges relate to three incidents in October and November last year. In one, naked prisoners were piled into a pyramid, an incident that became notorious when photos were published in April, provoking worldwide outrage.