The European Parliament has voted to launch an inquiry into claims that the CIA has been transporting suspects across Europe to secret prisons.
The US is facing growing pressure over CIA jail claims
The move is backed by leaders of all the political groups in the parliament.
It follows an inquiry by the Council of Europe that earlier this week said such allegations were credible.
The US has come under pressure over media claims that the CIA ran secret jails for terror suspects abroad and flew some through European airports.
The European Parliament's temporary investigative committee will run alongside the investigation by the human rights watchdog, the Council of Europe.
The committee's exact mandate is expected to be determined in January.
But MEPs say it should examine whether the CIA was involved in kidnapping and transporting terrorism suspects on European territory.
"It's important in this European Parliament that we get to the root of the matter," said Hannes Swoboda, one of the leaders of the Socialist group.
"We must investigate without prejudice but without being blind to the possibilities. We want to know the truth, nothing more than the truth," Mr Swoboda said.
Khaled al-Masri is suing the CIA for wrongful imprisonment and abuse
MEPs have also called for the committee to look at whether EU member states were involved or complicit in illegal detentions.
If any evidence of involvement is found, the parliament would open sanctions proceedings that could lead to the loss of EU voting rights, says the BBC's Alix Kroeger in Strasbourg.
Speaking to parliament before the vote, EU Justice Commissioner Franco Frattini warned that there was no evidence to confirm the allegations that had been made.
"Finding out the truth means getting evidence. No accusations can be considered founded without evidence," Mr Frattini said.
He added that in the absence of evidence he had to believe the denials from some European governments.
Germany on Wednesday denied any role in the abduction of its national Khaled al-Masri who says he was seized by US intelligence agents in 2003 and taken to Afghanistan, where he was held for five months and mistreated.
US Secretary of State Condoleezza Rice has said Washington would never condone torture, without categorically denying that some terror suspects were transported or held in Europe.