Council of Europe head Terry Davis said "appropriate action" would be taken against member states that did not take legal steps to prevent their airports being used for CIA flights of terror suspects or their territory for secret detention centers.

"If we discover such laws are not in place, or are inadequate, or are not effectively enforced, we will take appropriate action," Davis told a United Nations press conference in New York.

Davis warned the council's members that possible breaches of the European Convention on Human Rights would be dealt with but did not give details.

All of the Council of Europe's 46 member nations have reportedly returned questionnaires on the possible transport and interrogation of terrorism suspects by the US in Europe. In November, the body asked them to provide information detailing their degree of knowledge of alleged CIA flights and detention centers on European soil after allegations surfaced that the CIA was spiriting terror suspects away to countries where they might face harsh interrogation methods and possibly torture.

Five member nations -- Belgium, Bosnia, Georgia, Italy and San Marino -- missed the Feb. 21 deadline, Davis said. The answer of at least one nation was unsatisfactory and the responses of some others were brief, he said, but he refused to name them.

As many as 100 suspected cases of rendition

According to Swiss senator Dick Marty, who is leading the investigation into alleged renditions on behalf of the Council of Europe, at least 100 suspects were transferred through Europe by US agents to countries where they faced torture or ill treatment in recent years and it was highly likely that European governments knew about it.

Marty's preliminary report stated that there was no proof so far of the existence of clandestine detention centers in Romania or Poland as alleged by the New York-based Human Rights Watch.

However, Joanne Mariner, a terrorism and counterterrorism expert for Human Rights Watch (HRW), told a European Parliament committee on Thursday that the organization continued to believe that Washington had gone to great lengths to conceal any evidence of the alleged secret prisons and flights in Europe.

"The US government has taken every possible step to guard the secrecy of these activities," Mariner said and echoed Terry Davis' statement that European governments must ensure their military, intelligence and law enforcement officials answer all questions and provide all requested information.

Human Rights Watch accuses Washington of cover-up

Mariner acknowledged Marty's initial statement that hard evidence on secret prisons wasn't available and that concrete proof of CIA activities in Europe remained elusive.

She added that HRW had circumstantial evidence indicating the CIA transported suspected terrorists to Poland and Romania from Afghanistan, and she identified the two countries as possible hosts of secret US-run detention facilities. But Mariner admitted there was no direct proof that detainees were held in either country. Both countries have denied any involvement.

"There is circumstantial evidence they were held at one point in Poland and Romania ... It's based on flights records and other circumstantial evidence. There is very much that is in doubt," Mariner said. "There are daunting obstacles to carry out a meaningful investigation ... The present investigation will investigate acts that are covert and to which few persons are privy."

Flight logs raise questions of possible rendition

According to HRW, there are flight records pertaining to a Boeing 737, registration number N313P, which flew from Kabul, Afghanistan to northeastern Poland on Sept. 22, 2003, "during a period when some prisoners were secretly transferred from Kabul."

Mariner also gave other examples of planes that she said flew from Kabul to Romania and on to Morocco and Guantanamo. She said civilian planes would have "no reason to land at these airfields."

The Council of Europe is due to announce its response to the collected information from its 46 members at the beginning of March.