The CIA carried out clandestine flights to Europe, EU lawmakers said
The CIA has dismissed a Council of Europe report alleging that it ran secret jails for terror suspects in Europe after the 11 September attacks.
A CIA spokesman said the report was biased and distorted, and that the agency had operated lawfully.
Swiss Senator Dick Marty, who wrote the report, said secret CIA prisons "did exist in Europe from 2003 to 2005, in particular in Poland and Romania".
The charge was denied by both Polish and Romanian officials.
Former Polish President Aleksander Kwasniewski, who served from 1995 to 2005, said on Friday: "There were no secret prisons in Poland."
Romanian senator Norica Nicolai, who headed an investigation into the allegations, also denied his country's involvement.
"All statements made by Dick Marty are totally groundless," he said.
A spokesman for the CIA told the BBC that the agency's "operations have been lawful, effective, closely reviewed and of benefit to many people - including Europeans - by disrupting plots and saving lives".
Mr Marty - working on behalf of the Council of Europe, a human rights body - has been investigating the CIA's "extraordinary renditions" programme, under which terror suspects were transported around the world for interrogation.
In his report, he said a secret agreement among Nato allies allowed the CIA to operate the camps.
Unnamed CIA sources quoted by Mr Marty said Poland was the "black site" where eight "high-value detainees (HVDs)" were interrogated, including Khalid Sheikh Mohammed - alleged mastermind of the 9/11 attacks on the US in 2001.
The report says Romania "was developed into a site to which more detainees were transferred only as the HVD programme expanded".
"The secret detention facilities in Europe were run directly and exclusively by the CIA," the report says.
But it said "the highest state authorities" knew of the CIA's activities.
A report approved by a European Parliament committee earlier this year said more than 1,000 covert CIA flights had crossed European airspace or stopped at European airports in the four years after the 9/11 attacks.
US President George Bush admitted last year that terror suspects had been held in CIA-run prisons overseas, but he did not say where the prisons were located.