Politicians scrutinising illegal CIA activities in Europe also said incidents in which terror suspects were handed over to US agents did not appear to be isolated, and suspects were often transported in the same planes and by the same groups of people.

The preliminary report was compiled using data provided by the EU's air safety agency, Eurocontrol. It also used information gathered during three months of hearings and more than 50 hours of testimony by human rights groups and people who said they had been kidnapped and tortured by US agents.

Data showed CIA planes made numerous undeclared stopovers on European territory, violating an international air treaty requiring airlines to declare the routes and stopovers for planes on police missions, the Italian politician Giovanni Claudio Fava, who drafted the report, said.

"The routes for some of these flights seem to be quite suspect ... they are rather strange routes for flights to take. It is hard to imagine ... those stopovers were simply for providing fuel," he added.

Mr Fava referred to the alleged secret transfer of an Egyptian cleric abducted from a Milan street in 2003, a German who claimed he was transferred from Macedonia to Afghanistan, and the transfer of a Canadian citizen from New York to Syria among other suspect flights.

He said documents provided by Eurocontrol showed the plane transferring suspect Khalid al-Masri, a Kuwaiti-born German national, from Macedonia to Afghanistan in 2004 flew from Algeria to Palma de Mallorca, Spain, on January 22; from Palma de Mallorca to Skopje, Macedonia, on January 23, and from Skopje to Kabul via Baghdad overnight on January 24.

Earlier this year, Mr al-Masri told the European parliament committee he had been arrested by US intelligence agents on the Macedonian border while on holiday in December 2003.

He said he was taken to a hotel in Skopje and held there for several weeks before being flown to Kabul and put in prison for five months. He was then flown back to Europe in May 2004 and released in Albania.

Mr Fava said that, according to his investigations, the groups of agents on the flights were often the same, and it was unlikely that at least some EU governments - including those of Italy and Bosnia - would not have any information about the CIA operations investigated by the EU assembly.

The US has not made any public comments on allegations of secret renditions, and the official line by EU governments and senior EU officials is that there has been no irrefutable proof of such renditions.

The parliament inquiry began in January following media reports that US intelligence officers had interrogated al-Qaida suspects at secret prisons in eastern Europe following the September 11 2001 attacks on New York and Washington and transported some on secret flights that passed through Europe.

Clandestine detention centres, secret flights to or from Europe to countries in which suspects could face torture, or extraordinary renditions would all breach the continent's human rights treaties.

The focus of the inquiry soon changed from secret prisons in Europe to rendition flights as people who said they were abducted by US agents gave detailed accounts of their transfers to what they said were secret detention centres in the Middle East, Asia and northern Africa.

The British government has admitted that aircraft suspected of being used by the CIA for "extraordinary rendition" had passed through British airports on 73 occasions since 2001.

They included an aircraft that left the Afghan capital, Kabul, in November 2002 and landed in Edinburgh before continuing its journey to Washington.

Earlier this month, the human rights group Amnesty International released a report detailing almost 1,000 flights directly linked to the CIA through "front" companies, most of which it said had used European air space.

A further 600 CIA flights were made by planes hired from US aviation companies.

The report carried details of more than 200 alleged CIA flights passing through British airports, and called for an independent public inquiry into all aspects of UK involvement in extraordinary rendition flights.

It claimed the US made efforts to ensure conditions and locations in which detainees were held were kept secret.

Four of the CIA's 26 planes have landed and taken off from British airports more than 200 times over the past five years, Amnesty said. The airports included Stansted, Gatwick, Luton, Glasgow, Prestwick, Edinburgh, Londonderry and Belfast.

RAF Brize Norton, in Oxfordshire, Biggin Hill, in Kent, and RAF Leuchars, in Scotland, were among others used along with the Turks and Caicos islands, a British overseas territory in the Caribbean.