Council of Europe Chairman Terry Davis urged European countries to provide full information on the issue, joining a formal probe the body launched two weeks ago. Austria's air force was investigating allegations that a CIA transport plane containing suspected terrorist captives flew through the neutral country's airspace in 2003, and Denmark said it would ask U.S. authorities for details about the alleged transport of detainees on planes said to be used by the CIA over Danish territory.
Bulgaria was the latest country to deny reports of involvement, saying the CIA's planes never landed at the Sarafovo airport near the Black Sea port of Burgas as alleged by the media.
The flights have become an issue in amid reports that U.S. intelligence may have transported suspected al Qaeda members and others through Europe en route to secret prisons in eastern Europe and other countries for interrogation.
Allegations the CIA hid and interrogated key al Qaeda suspects at Soviet-era compounds in Eastern Europe were first reported in The Washington Post on Nov. 2. The paper did not name the countries involved.
A day later, Human Rights Watch said it had evidence indicating the CIA transported suspected terrorists captured in Afghanistan to Poland and Romania. The New York-based group identified the Kogalniceanu military airfield in Romania and Poland's Szczytno-Szymany airport as possible sites for secret detention centers, saying it based its conclusions on flight logs of CIA aircraft from 2001 to 2004.
Speaking in Strasbourg, France, Davis said that due to the serious nature of the allegations, he had sent a letter to the governments of the Council of Europe's 45 member states demanding information on how their law ensures that acts by foreign agencies within their jurisdiction are subject to adequate controls.
Austria's air force chief Erich Wolf told Austrian state broadcaster ORF that a CIA transport plane that took off from Frankfurt, Germany, and headed to Azerbaijan crossed Austrian airspace on Jan. 21, 2003.
Austria's air force scrambled fighter jets to make contact with the plane's pilot, but did not suspect anything wrong at the time and lodged no diplomatic protests, Wolf said. "There was no sign of an airspace abuse," he said.
Since then, however, Austrian authorities have found reason to believe the flight was transporting suspected terrorists, Wolf added. He did not elaborate.
On Tuesday, Swiss senator Dick Marty, who leads the Council of Europe probe, said he was investigating 31 suspect planes that landed in Europe in recent years, and was trying to acquire past satellite images of sites in Romania and Poland. He said that despite lack of proof, there were "many hints, such as suspicious moving patterns of aircraft, that have to be investigated."
Other airports that might have been used by CIA aircraft in some capacity include Palma de Mallorca in Spain, Larnaca in Cyprus and Shannon in Ireland, as well as the U.S. air base at Ramstein, Germany, Marty said in a report.
Swedish authorities, meanwhile, have confirmed at least one plane with alleged CIA links landed in Sweden three times since 2002. Denmark says 14 flights with suspected CIA ties entered its airspace since 2001; Norway has confirmed three such flights; and Icelandic media have reported 67 landings.
There have been other unconfirmed reports in Macedonia and Malta.