The International Committee of the Red Cross (ICRC) called on Thursday for access to all foreign terrorism suspects held by the United States after a report of a covert CIA prison system for al Qaeda captives.
The Washington Post said on Wednesday the CIA had been hiding and interrogating inmates at a secret facility in Eastern Europe, among so-called "black sites" in eight countries under a global network set up after the September 11, 2001 attacks.
"We are concerned at the fate of an unknown number of people captured as part of the so-called global war on terror and held at undisclosed places of detention," Antonella Notari, chief ICRC spokeswoman, told Reuters in response to a question.
"Access to detainees is an important humanitarian priority for the ICRC and a logical continuation of our current work in Afghanistan, Iraq and Guantanamo Bay," she added.
Also in Geneva, the United Nations' Human Rights Committee said it had received two letters and a report from the United States which it hoped would address the issue of detainees being held outside the country.
"It was in our request to the United States. We are going to see how they answer," committee chairwoman Christine Chanet for France told journalists, saying the committee had yet to study the documents.
The European Commission said on Thursday it would look into media reports naming two east European countries as allowing the CIA (US Central Intelligence Agency) to hold al Qaeda suspects outside of any national or international legal jurisdiction.
Friso Roscam Abbing, spokesman for European Justice and Security Commissioner Franco Frattini, said the EU executive would check the reports with Poland, a new member state, and Romania, which is due to join the European Union in 2007.
The US-based campaign organisation Human Rights Watch said earlier it had indications the two were hosting CIA prisons.
Both denied the allegations on Thursday and the Commission's Abbing said it had no knowledge of any such prisons at present.
"What I think we will do is to at a technical level... check what the truth is in these stories. We will check the accuracy of those reports," he told a daily briefing.
He said the treatment of prisoners was not a matter of EU competence but any secret prisons would not appear compatible with the EU's non-binding Charter of Fundamental Rights or the so-called Copenhagen political criteria for EU membership, which include upholding the rule of law and respect for human rights.
He said the Commission's decision to check the reports did not signal any formal investigation, nor would it be appropriate for Frattini to personally question government leaders in the countries concerned.
Carroll Bogert, associate director of the New York-based Human Rights Watch, outlined earlier what had led the group to believe Poland and Romania were hosting the alleged CIA prisons.
She said the group based its assumption on flight logs, such as a Boeing 737 having made trips to eastern Europe from Afghanistan and countries in the Middle East.
One flight log showed that a plane went from Kabul to north-eastern Poland on September 22, 2003. That was the same month that "we know several CIA prisoners who were held in Afghanistan were transferred out of Afghanistan and the next day the same plane landed at a military airport in Romania," Bogert said.
The Romanian airfield had been closed to the public and the media for some time, she added.
The Washington Post said it had not published the names of the European countries at the request of senior US officials who said disclosure could disrupt counterterrorism efforts or make the host countries targets for retaliation.
US officials declined direct comment on the report, which was likely to stir up fresh criticism of the Bush administration's treatment of terrorism suspects.
Russia's FSB security service and Bulgaria's foreign ministry both denied such facilities existed on their territory as did Thailand, which was named in the Washington Post report.
The UN's Human Rights Committee monitors a 1976 treaty on basic freedoms. The regular report on compliance filed by the United States last Friday was some seven years overdue.
The committee, which will examine the report next July at a public session, said last year it had specifically asked that the issue of detention centres be included.
The ICRC, a neutral humanitarian organisation, monitors whether prison conditions and treatment of detainees comply with the 1949 Geneva Conventions, which lay down rules for treating those captured in international armed conflicts.