A United Nations human rights expert expressed grave concerns on Thursday that the CIA may continue using torture on terrorism suspects at Guantanamo Bay.

Martin Scheinin, U.N. special rapporteur on protecting human rights while countering terrorism, said the behavior of CIA officials he met on a visit to the U.S. detention facility at Guantanamo Bay in Cuba last week only strengthened his suspicions.

"They were participants in one of my meetings but they failed to answer any single question in a substantive, meaningful way, which only confirmed the suspicions that they have too much to hide," Scheinin told a news briefing in Geneva.

The Finnish law professor said currently about 300 detainees were still being held at Guantanamo, almost all of them without prosecution.

He suspected that the CIA intend to keep the detainees at Guantanamo without trial in order to hide their methods of interrogation that are incompatible with international law.

Scheinin also expressed concern at recent revelation that the CIA had destroyed videotapes showing the interrogation of terror suspects.

"It is one more argument that supports the contention that the CIA has been involved and continues to be involved in the use of interrogation techniques that violate the absolute prohibition against torture," he said.

Scheinin presented on Wednesday a report to the U.N. Human Rights Council, in which he expressed grave concern about the situation of detainees held at Guantanamo Bay and the lack of judicial guarantees and fair trial procedures.

He also called on the United States to close the Guantanamo facility and make decisions on what to do with the remaining detainees as soon as possible.