The CIA called the report "distorted," but stopped short of denying the existence of prisons in the two countries -- the agency said it does not discuss the location of its overseas facilities. Poland and Romania also vehemently denied the allegations.

"High value detainees" like self-proclaimed 9/11 mastermind Khalid Sheikh Mohammed and suspected senior al-Qaida operative Abu Zubaydah were held in Poland, said the report, which cited CIA sources. It said lesser detainees, but still of "remarkable importance," were taken to Romania.

Swiss senator Dick Marty, who is heading the investigation into alleged CIA prisons in Europe, gestures as he speaks during a press conference at the Council of Europe office in Paris Friday, June 8, 2007. [AP]

Top officials in both countries knew of the detention centers, said the report by Swiss Sen. Dick Marty, a former prosecutor asked by the Council of Europe, a human rights watchdog, to investigate CIA activities after media reports of secret prisons emerged in 2005.

Marty did not rule out the CIA having more such prisons in Europe, but told reporters he did not include that in his report because his sourcing was insufficient. He accused Germany and Italy of obstructing investigations into secret detentions.

The report said its conclusions about the clandestine prisons relied on "multiple sources which validate and corroborate one another." Marty said his team spoke with "over 30 one-time members of intelligence services in the United States and Europe" as well as former or current detainees and human rights activists.

While conceding at a news conference that sources for the report were limited, Marty said they were "well placed," including some who "were implicated."

The alleged prisons were at the center of a "spider's web" of purported human rights abuses that Marty outlined in his initial investigation a year ago. That report focused on flights to spirit detainees to CIA hideouts with landing points in at least 14 nations.

He said he saw his reports as a "dynamic of truth" and hoped they will stir debate over what he charges were blatant abuses of human rights.

Clandestine prisons and secret CIA flights involving European countries would breach the continent's human rights treaties, although the Council of Europe has no power to punish countries. The council, which is separate from the European Union, was set up four years after World War II to promote democracy, human rights and the rule of law in Europe.

Officials at the EU have said previously that they trust the denials of Poland and Romania about hosting secret jails.

CIA spokesman Paul Gimigliano did not address whether there were secret detention centers, but he disputed the report's characterization of the agency's activities.

"When you see words like apartheid and torture in the document, that tells you it's biased and distorted," he said. "The CIA's counterterror operations have been lawful, effective, closely reviewed and of benefit to many people ¡ª including Europeans ¡ª in disrupting plots and saving lives. Our counterterror partnerships in Europe are very strong."

Following a meeting with President Bush in Gdansk, Polish President Lech Kaczynski told reporters: "I know nothing about any CIA prisons in Poland." His predecessor, Aleksander Kwasniewski, who was president in 2001-05, said: "I deny it. I've said as much several times."

Former Romanian President Ion Iliescu, mentioned in a list of ranking officials who allegedly had knowledge of the prisons, dismissed Marty's report as "stupid."

The report, which did not give specific locations for the alleged jails, provided graphic descriptions of conditions.

It told of prisoners being kept naked for weeks, sometimes attached to a "shackling ring" in cells. Buckets served as toilets. Masked guards who never spoke were the only contact for those consigned to four-month isolation regimes.

Cells, sometimes equipped with video cameras, were cramped and kept extremely hot or cold, the report said. Prisoners had to listen to irritating noises, including "torture music," rock or rap as well as "distorted" verses of the Quran, it said.

Bush acknowledged the existence of a secret detention program last September, when he announced the CIA had moved Sheikh Mohammed and 13 other suspected terrorists to the US prison at Guantanamo Bay.

Marty's report said Poland and Romania hosted secret prisons under a special post-Sept. 11 CIA program to "kill, capture and detain" key terrorist suspects. It said the jails grew out of a secret pact within NATO shortly after the terror attacks on the US

The pact "allowed the CIA to be able to move around Europe unobstructed, without undergoing any control and, especially, the NATO (security) protocol on secrecy was applied," Marty said.

In Italy, the first trial stemming from the CIA's detention program opened Friday without the presence of any of the 26 Americans charged with the 2003 kidnapping of a Muslim cleric suspected of terrorist ties. The trial has irritated US-Italian relations and its opening coincided with Bush's arrival in Rome.