The Council of Europe has appointed Swiss politician Dick Marty to investigate allegations that the CIA set up secret prisons in eastern Europe for terror suspects.
Last week the United States media reported that the intelligence agency had been hiding and interrogating some of its most important al-Qaeda captives at Soviet-era compounds.
The Council – which acts as a human rights watchdog – made the appointment via its parliamentary assembly's legal affairs committee on Monday.
In a statement the committee said Marty, a senator from the Italian-speaking canton of Ticino, had been asked to "examine the subject of alleged secret CIA detention centres with a view to a possible urgent debate at the next Standing Committee's meeting".
This will take place in Bucharest, Romania, on November 25.
The committee also urged the Council's secretary-general to ask the organisation's 46 member states to provide Marty with any information they may have on the subject. Marty is also authorised to visit certain member states if need be.
The statement said the committee's director, René van der Linden, had stressed last week that all member states were under a legal obligation to respect the European Convention on Human Rights.
Report in January
The Council has already stated that such prisons would constitute a human rights violation.
Marty, who is also a former Ticino state prosecutor, said he would start his investigation by requesting information on the issue on all Council member states.
"I'm hoping that a comprehensive report could be presented in January," he told the Associated Press news agency.
"So far, all we have is a suspicion. There have been certain reports and they must be investigated," he added.
The investigation comes after the Washington Post newspaper last week claimed that the CIA had been holding al-Qaeda terror suspects at detention centres in eastern Europe.
In addition, Human Rights Watch said it had evidence indicating that the CIA had transported suspected terrorists captured in Afghanistan to Poland and Romania.
Some governments in the former Soviet bloc, including Poland and Romania, have already denied the allegations. The European Union and the Swiss-run International Committee of the Red Cross (ICRC) have also indicated that they would look into the issue.
The ICRC, which has had exclusive rights to visit terror suspects detained at a US military base at Guantanamo, said it had asked Washington about the allegations and requested access to the prisons if they exist.
Spokeswoman Antonella Notari said the ICRC, which also monitors conditions at US detention centres in Afghanistan and Iraq, has been unable to find some people who have reportedly been detained.
She was quoted in the Associated Press as saying the ICRC was "concerned about the fate of an unknown number of persons detained as part of what is called the "global war on terror" and held in undisclosed places of detention."
The Washington Post reported that the centres – known as "black sites" – were set up in the wake of the September 11 attacks in 2001.
About 30 detainees were held by the CIA at these sites, alleged the newspaper. A further 70 detainees had been handed over to the intelligence services in Egypt, Jordan, Morocco, Afghanistan and other countries, it was reported.
The newspaper said that all sites had now been closed. The CIA has so far refused to comment and the White House has not confirmed the claims.
swissinfo with agencies
The Council of Europe is the continent's oldest political organisation, founded in 1949.
It groups together 46 countries, including 21 countries from central and eastern Europe.
It is distinct from the 25-nation European Union, but no country has ever joined the EU without first belonging to the Council.
The Council, based in Strasbourg, France, defends human rights and parliamentary democracy.