The US spy agency CIA is operating a covert prison system covering eight countries for holding terror suspects, The Washington Post reported Wednesday.

The system was set up by CIA nearly four years ago and has at various times included sites in Thailand, Afghanistan and several Eastern European countries as well as the US naval base in Guantanamo Bay, Cuba, said the newspaper.

Quoting foreign and diplomatic sources, it said the hidden system is a central element in the CIA's war on terror which depends on the cooperation of foreign intelligence services and on keeping even basic information about the system secret from most US and foreign officials as well as US lawmakers overseeing the spy agency's covert actions.

The existence and locations of these prisons -- 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, according to the newspaper.

The CIA and the White House, citing national security concerns and the value of the program, have dissuaded the US Congress from demanding that the agency answer questions in open testimony about the conditions under which captives are held, it said.

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, according to the newspaper.

While exposure of abuses in Iraq's Abu Ghraib prison and other overseas detention facilities of the US military have forced the Pentagon to conduct investigations and punish several soldiers, the CIA has not even acknowledged the existence of its secret prisons, it said.

However, there is growing concern among US lawmakers, foreign governments and human rights groups about the opaque CIA system, according to the newspaper.

Source: Xinhua