The move comes after a probe by the Council of Europe, a separate 46-member rights body, concluded that allegations of secret CIA prisons were credible and that the US seemed to have illegally abducted and detained individuals.

The European Parliament will decide in mid-January on the make-up of the investigating commission and the length of its mandate, said an official at the European Union's legislature, speaking on condition of anonymity.

"It's important in this European Parliament that we get to the root of the matter," said Hannes Swoboda, vice president of the Socialist group in the assembly.

"We must investigate without prejudice but without being blind to the possibilities. We want to know the truth, nothing more than the truth. If we do this then we are genuinely battling against terrorism but also against torture," he added.

British Prime Minister Tony Blair on Wednesday dismissed as "completely absurd" calls to probe all US government plane movements through Britain in the wake of the CIA "extraordinary rendition" row.

Blair said there were a "whole series of reasons" why Washington requested stops at British airports and restated his government's opposition to torture and lack of knowledge about so-called "extraordinary rendition" flights.

Council of Europe discovers credible information

However, the Council of Europe probe concluded that "the information gathered to date reinforced the credibility of the allegations concerning the transport and temporary detention of detainees -- outside all judicial procedure -- in European countries."

It said that some European governments may have colluded.

Dick Marty, the Swiss parliamentarian leading the inquiry, said the fact that US Secretary of State Condoleezza Rice had failed to categorically deny that detainees were transported or held in Europe substantiated the claims.

The council's findings will intensify pressure on the United States to explain its policy on terror suspects.

EU states open own investigations into CIA missions

Meanwhile Warsaw promised to fast-track its own probe into whether Poland housed the US intelligence agency's main European base for interrogating terror suspects.

The Swiss parliament has also opened an inquiry into flights over the tiny landlocked nation by CIA-chartered aircraft thought to be carrying suspected terrorists, a parliamentary commission said in a statement Wednesday.

Over the next few weeks, the commission is to probe how much the government knew about the flights, what steps it took and the level of Swiss intelligence involvement.

Turkey on Sunday denied the United States' CIA spy agency interrogated suspected terrorists on Turkish soil.

German detainee investigation continues with denials

In Germany, Foreign Minister Frank-Walter Steinmeier said that German authorities played no role in the abduction of a German man of Lebanese descent seized in Macedonia and held for five months in Afghanistan.

The case of Khaled el Masri has fuelled the controversy over the alleged secret prisons run by the CIA and prisoner flights through Europe.

Steinmeier told parliament that the German authorities were only informed of Masri's abduction in June 2004, after he had been released in Albania by his captors.

Masri last week filed a lawsuit against the CIA in a US federal court, alleging that he was wrongfully abducted and abused as a prisoner.

Masri has also stated that he was questioned by Germans while being held in Afghanistan. More questions about the level of involvement of the German authorities in such cases have been raised by a detainee at the US military prison at Guantanamo Bay.