The Swiss investigator looking into claims of secret CIA prisons in Europe has said that people were apparently abducted and transferred between countries.
Dick Marty told the Council of Europe on Tuesday that he deplored the fact that "no information or explanations" were provided by the United States government.
"Legal proceedings in progress in certain countries seemed to indicate that individuals had been abducted and transferred to other countries without respect for any legal standards," the Swiss senator said, while presenting his findings in Paris.
As current chairman of the Council's legal affairs committee, Marty has been empowered to head the investigation by the human rights body.
He is investigating claims that the Central Intelligence Agency transferred prisoners through European airports to secret detention centres, actions that would breach the human rights principles of the Council's member states.
Poland and Romania have been identified by the New York-based Human Rights Watch as sites of possible CIA secret prisons, but both countries have repeatedly denied any involvement.
Marty added in his report that it was "still too early to assert that there had been any involvement or complicity of member states in illegal actions".
The Swiss authorities confirmed three days ago that a small jet chartered by the CIA flew over Switzerland 19 times since the start of 2003.
A plane was recorded on the day a radical imam was allegedly abducted in Italy and flown to Germany, but the Swiss aviation office does not know whether the man was on board.
Marty was critical of the US for not formally confirming or denying the allegations.
He criticised Washington's lack of cooperation in reference to a recent European visit by US Secretary of State Condoleezza Rice, who refused to answer repeated questions about the allegations.
Marty has requested air traffic logbooks to try to determine flight patterns of several dozen suspected CIA airplanes.
He has also requested satellite pictures of the Sczytno-Szymany airport in northeastern Poland and the Mihail Kogalniceanu Air Base in eastern Romania, after they were identified by Human Rights Watch as possible sites of clandestine CIA detention centres.
swissinfo with agencies
The Washington Post reported on November 2 that the US has used "Soviet-style" prison camps to interrogate suspected terrorists in eastern Europe, most likely Poland and Romania.
US Secretary of State Condoleezza Rice has labelled the movement of suspected terrorists as "renditions".
Switzerland's Federal Civil Aviation Office has said that a small jet chartered by the CIA and suspected of ferrying political prisoners has flown over Switzerland 19 times since the start of 2003.
The Council of Europe is Europe's oldest political organisation, founded in 1949.
It comprises 46 countries, including 21 from eastern and central Europe.
The Strasbourg-based Council is independent from the 25-nation European Union.
The Council defends human rights and parliamentary democracy.