Just days after the US Justice Department closed its investigation into the CIA's torture and abuse of detainees, non-governmental organisation Human Right Watch (HRW) says it has collected extensive evidence of torture perpetrated by US authorities during the Bush administration.
The torture was allegedly perpetrated against exiled opponents of late Libyan leader Muammar Gaddafi, suspected of carrying out terrorist activities.
In a report entitled Delivered into Enemy Hands: US-Led Abuse and Rendition of Opponents to Gaddafi's Libya, HRW details interviews with14 former prisoners who were allegedly arrested and detained without charge by the CIA - in some cases with the help of the UK's MI6.
Khalid al-Sharif, one of the detainees interviewed by HRW, said: "I spent three months getting interrogated heavily. They gave me a different type of torture every day. Sometimes they used water, sometimes not.... Sometimes they stripped me naked and sometimes they left me clothed."
The detainees' stories are supported by secret documents HRW found abandoned in the offices of former Libyan intelligence chief Musa Kusa, after Tripoli fell to rebel forces.
The documents suggest that the suspected Islamic fundamentalists were tortured and questioned before being handed over to Gaddafi's police and locked up in Libyan prisons.
"Not only did the US deliver Gaddafi his enemies on a silver platter, but it seems the CIA tortured many of them first," said Laura Pitter, counterterrorism advisor at HRW and author of the report.
The documents suggest the US and the UK had close intelligence links with the Gaddafi regime, with whom they cooperated to crackdown on Islamic militants after 2003.
The majority of the detainees belonged to the Libyan Islamic Fighting Group (LIFG), which worked to overthrow Gaddafi for 20 years.
Some were released from jail as a result of the Libyan revolution and joined the NATO-backed anti-Gaddafi rebels in the 2011 conflict.
According to HRW at least two of the 14 prisoners were waterboarded or exposed to similar water tortures.
Waterboarding is a form of simulated drowning obtained by pouring water on a hooded detainee's nose and mouth. The technique is widely considered a form of torture.
The allegations appear to contradict the US government's official accounts, according to which waterboarding was used on prisoners held in US custody just three times - all of them involving senior al-Qaida suspects.
"It opens up the question of just how broad the torture program was. If the assertion that only three detainees were waterboarded is untrue, then it begs the question of what else was said with assertion officially that misrepresented the breadth of the torture," said Karen Greenberg, director of center on national security at Fordham Law School.
The report continues: "Other abuses reported by these former detainees include being chained to walls naked - sometimes while diapered - in pitch black, windowless cells, for weeks or months; restrained in painful stress positions for long periods, forced into cramped spaces; beaten and slammed into walls; kept indoors for nearly five months without the ability to bathe; and denied sleep by continuous, very loud Western music."
Pitter added: "The scope of Bush administration's abuse appears far broader than previously acknowledged and underscores the importance of opening up a full-scale inquiry into what happened."
The CIA refused to comment on the specific allegations.