The CIA shut down two secret prisons in eastern Europe last month after human rights activists said they were located in Poland and Romania, according to a US television news report.
Citing "current and former CIA officers" ABC News said the agency scrambled to move 11 al-Qaeda suspects in the secret jails to north Africa before US secretary of state Condoleezza Rice arrived in Europe this week.
The report said that all but one of the 11 detainees were subjected to "enhanced interrogation techniques" including "waterboarding", which involves strapping a suspect to a board, covering his face with cellophane and pouring water on it, simulating the experience of drowning.
CIA sources told ABC News that the secret prison system began in March 2002 with the capture of Abu Zabayda in Pakistan. After treatment there for gunshot wounds, he was taken to Thailand where a doctor sent from CIA headquarters in Langley, Virginia, supervised his medical treatment.
When he recovered, he was made to stand for hours in a cold cell and finally handcuffed and strapped, feet up, to a water board until after 31 seconds he begged for mercy and began to co-operate.
At the CIA's request, ABC News did not name the European countries where the secret prisons were cited but said that all 11 prisoners were at one stage held at "a former Soviet air base in one eastern European country".
Polish defence minister Radoslaw Sikorski told ABC correspondent Brian Ross: "My president has said there is no truth in these reports."
Mr Ross asked: "Do you know otherwise, sir? Are you aware of these sites being shut down in the last few weeks, operating on a base under your direct control?"
Mr Sikorski answered: "I think this is as much as I can tell you about this."
The CIA sources said that the secret prison system was related to the practice of "rendition", transferring detainees to third countries for interrogation.
They said that Jordan, Syria, Morocco and Egypt were among the nations used in order to extract confessions quickly using techniques harsher than those authorised for use by US intelligence officers.
The CIA would be forbidden from using "enhanced interrogation techniques" under a proposal from Senator John McCain to outlaw the use of torture by US government personnel anywhere in the world.
The White House has pressed legislators to exempt the CIA from the measure, which would ban cruel and inhumane treatment of suspects and require interrogators to rely on an army field manual that complies with standards set by the Geneva Conventions.
The Senate voted 90-9 in favour of the McCain proposal, which takes the form of an amendment to an annual defence spending Bill, and the House of Representatives is expected to back the measure if it is linked to another proposal that would limit Guantanamo Bay detainees' access to US courts.
President George W. Bush insists that the US does not torture prisoners but has threatened to veto the defence spending Bill if it includes the McCain measure.