Secret CIA planes used for the transport of terrorism suspects stopped off at Shannon Airport on 50 occasions over the past four years, Amnesty International said in a statement this evening.
The human rights group claimed it had obtained flight records showing some 800 flights involving six planes used by the CIA to transport terror suspects between September 2001 and September 2005.
US planes involved in the "war on terror", particularly the US campaigns in Afghanistan and Iraq, routinely land in Shannon but only have permission to carry non-military personnel. However, protest groups say uniformed troops are often aboard these flights.
Amnesty claims that evidence of the involvement in renditions of flights though Shannon contradicts assurances given last week by the US Secretary of State Condalezza Rice to Minister for Foreign Affairs Dermot Ahern.
Mr Ahern said he accepted the assurances but the Government "would be very concerned" if Shannon were used for purposes that involved a breach of human rights.
"We would take action if we thought that was the case," he said after meeting Ms Rice in Washington last week.
Amnesty today rejected assertions by Ms Rice today that transferring detainees from without legal process was permissible under international law.
"Flying detainees to countries where they may face torture or other ill-treatment is a direct and outright breach on international law with or without so called "diplomatic assurances".
"These assurances are meaningless. Countries known for systematic torture, regularly deny the existence of such practices," said Claudio Cordone, Amnesty International's senior director of regional programmes.
Amnesty said it obtained US Federal Aviation Administration flight records showing six CIA-chartered planes landed 50 times in Shannon and took off 35 times. Amnesty said the disparity suggests some flights were kept secret.
It also said none of the planes were military transport craft. The CIA is suspected of using shell companies to operate planes carrying terror suspects in a bid to hide its activities.
A Gulfstream jet IV, call sign N85VM (later re-registered N227SV) transported a man kidnapped in Italy to Egypt from Germany and then flew to Shannon. The plane's flight log also shows visits to Afghanistan, Morocco, Dubai, Jordan, Italy, Japan, Switzerland, Azerbaijan and the Czech Republic, Amnesty says.
The organisation said it was publishing its information in response to a challenge form from Mr Ahern last Thursday to produce evidence.
It said that international law requires all states refrain from assisting in human rights abuses and called on European countries to investigate allegations that their territory has been used to assist CIA-chartered flights secretly transporting detainees to countries where their rights may be abused.