"There are no secret detention facilities located on Camp Bondsteel (eastern Kosovo)," Major Michael Wunn, US military spokesman in Kosovo, told news agency AFP in reference to the US base as part of NATO forces in the Balkan province.

The major was responding to comments Friday by Council of Europe Human Rights Commissioner Alvaro Gil-Robles, who claimed to have seen Muslims being held at a facility in Kosovo which looked like the Guantanamo Bay prison in Cuba, used to house captives from the US-led "war on terror." Gil-Robles told France's Le Monde newspaper he had been "shocked" by conditions at the center, which he said he witnessed in 2002.

Major Wunn said it was "common knowledge" that Camp Bondsteel included a detention facility used to house people detained during NATO peacekeeping operations in the UN-administered southern Serbian province. But he said it was currently empty and it was not used as a secret prison by the Central Intelligence Agency.

"The facility is operated by US military police soldiers fully trained in detention center operations. Currently, no one is detained in this facility," he said. "The facility is subject to inspection by the International Committee of the Red Cross (ICRC) and is regularly inspected by the United States Army, Europe."

Washington under pressure

The denial came as Washington felt mounting European pressure to reveal the routes and activities of its CIA prisoner flights amid concerns about human rights abuses and torture on European territory. Reports of CIA plane touch-downs have come from countries as far apart as Macedonia, Finland and Portugal in recent weeks.

The Council of Europe opened a probe this week, but top investigator Dick Marty, of Switzerland, conceded Saturday that he had "practically no methods of constraint" to stop the flights to change CIA methods.

The council's member states have until Feb. 21 to provide information to the inquiry, which will examine governments' compliance with European human rights law and whether officials have been involved in "unacknowledged" detentions or transport of detainees.

"The Council of Europe cannot adopt specific measures against the United States," Marty told The Times newspaper in Geneva. But he said Washington could be made to feel an "international reproach" and explain itself before the United Nations.

European governments have expressed concern over reports that the CIA flights could be used to transport prisoners, held without charge as "enemy combatants," to secret torture sites outside US legal jurisdiction.

"Those responsible must pay"

European Union foreign policy chief Javier Solana told Spanish radio on Saturday that Europeans found any suggestion of torture "intolerable" and insisted that such reports be investigated.

"I have no doubt that this will be the object of an investigation... It must be investigated and those responsible must pay," he told Cadena Ser radio.

Meanwhile, Turkish Transport Minister Binali Yildirim confirmed that a CIA plane had "put down" at the Sabiha Gokcen airport in Istanbul last week in order to refuel.

"There was a landing requested for technical reasons. Its landing was authorized. It was not carrying any passengers -- only equipment was on board," the minister was quoted as saying by the Anatolia news agency. "It filled its tanks with fuel and continued in its way," he said, adding that when planes requested landings to refuel it was difficult to refuse them.