WASHINGTON, Nov 2: The CIA has been hiding and interrogating some of its most important Al Qaeda captives at a Soviet-era compound in east Europe, the Washington Post reported on Wednesday.

Quoting US and foreign officials familiar with the arrangement, the Post said that the secret facility was part of a covert prison system set up by the CIA nearly four years ago. At various times, it has included sites in eight countries, including Thailand, Afghanistan and several countries in east Europe, as well as a small centre at the Guantanamo Bay prison in Cuba.

The Post said that this hidden global internment network is a central element in the CIA’s unconventional war on terrorism. It depends on the cooperation of foreign intelligence services, and on keeping even basic information about the system secret from the public, foreign officials and nearly all members of Congress charged with overseeing the CIA’s covert actions.

The existence and locations of the facilities — referred to as ‘black sites’ in classified White House, CIA, Justice Department and congressional documents — are known to only a handful of officials in the United States and, usually, only to the president and a few top intelligence officers in each host country, the Post said.

The CIA and the White House have dissuaded Congress from demanding that the agency answer questions in open testimony about the conditions under which captives are held.

“Virtually nothing is known about who is kept in the facilities, what interrogation methods are employed with them, or how decisions are made about whether they should be detained or for how long,” the report said.

Last month, Vice President Cheney and CIA Director Porter J. Goss asked Congress to exempt CIA employees from legislation already endorsed by 90 senators that would bar cruel and degrading treatment of any prisoner in US custody.

The Washington Post did not publish the names of the east European countries involved in the covert programme, at the request of senior US officials. They argued that the disclosure might disrupt counter-terrorism efforts in those countries and elsewhere and could make them targets of possible terrorist retaliation.