The US Central Intelligence Agency (CIA) ran at least two secret detention facilities in the Baltic nation of Lithuania, a parliamentary inquiry has found.
The sites were set up by Lithuanian intelligence services for the CIA, according to the report published on Tuesday.
But the head of the inquiry said he was not able to confirm whether al-Qaeda suspects had ever been interrogated at either location.
"The sites existed ... and planes landed," Arvydas Anusauskas, the head of parliament's national security and defence committee, told reporters.
"Regarding the 'cargo', I can't confirm anything, because Lithuanian authorities could not carry out the usual checks, so what was being transported was unknown."
Lithuania's parliament called for an investigation after the US television channel ABC alleged that the former Soviet republic had hosted a CIA "black site" for a small number of captives.
ABC News said that the facility near the airport in Vilnius, the Lithuanian capital, operated from early 2004 to late 2005 and that CIA aircraft brought high-level al-Qaeda suspects to the jail.
"The first project was developed from 2002. In response to the wishes of our partners and the conditions that were imposed, the site was meant to host one person. The second site was created in 2004," Anusauskas said.
The second site is believed to have been a converted riding school in the hamlet of Antaviliai, about 20km from Vilnius. It was purchased in March 2004 by a US-registered firm Elite LLC, which is purportedly a CIA front.
"The lay-out of the buildings, their secret nature, the fence around the site, plus the only sporadic visits by VSD [Lithuanian intelligence service] operatives, enabled our partners to carry out activities without VSD control and to use the place however they liked," Anusauskas said.
The investigation also found that five aircraft linked to the CIA landed in Lithuania between 2003 and 2006, and that local intelligence officials prevented customs and border guards from inspecting them.
Anusauskas said that senior officials were not informed about the secret jails and there had been no government approval given for the sites.
"The biggest concern comes from the fact that a few agents, without consulting the head of state, took a decision that breached the law," he said, adding that "the VSD became a state within a state".
Valdas Adamkus, who was president for much of the period that the secret facilities operated, dismissed the findings.
"I am certain this never happened and nobody proved me wrong," he told the Baltic News Service.
But Andrius Kubilius, the Lithuanian prime minister, said it was "a matter of great concern" that such infrastructure existed and that it could be possible to detain suspected terrorists without government control.
In a 2007 investigation, conducted on behalf of the Council of Europe, Dick Marty, a Swiss politician accused 14 European governments of permitting the CIA to run detention centers or carry out rendition flights between 2002 and 2005.
This video was broadcast by Russia Today on Dec. 22, 2009.