GENEVA - UN rights experts called Thursday for action and prosecutions to end the secret detention of terror suspects, in which it alleges 66 countries including the United States are involved.

The experts on torture, counter-terrorism and enforced disappearances said the 66 countries they had named in a January report must investigate the covert imprisonment of alleged terror suspects.

The report warned that the "widespread and systematic" secret detentions could pave the way for charges of crimes against humanity against the countries concerned.

It listed 66 countries allegedly involved and called on governments to prosecute those who ordered such detentions.

"International law clearly prohibits secret detention, which violates a number of human rights and humanitarian law norms that may not be derogated under any circumstances," said the report.

"Resorting to secret detention effectively means taking (detainees) outside the legal framework and rendering the safeguards contained in international instruments, most importantly habeas corpus, meaningless," it added.

In a debate Thursday on the report, the experts urged the UN Human Rights Council to take action.

"We think this is enough evidence that the council should take action," said Manfred Nowak, the UN special rapporteur on torture.

A summary of the debate said "secret detention should be explicitly prohibited along with all other forms of unofficial detention."

"In almost no recent cases have there been any judicial investigations into allegations of secret detentions and practically no one has been brought to justice."

The UN special rapporteur on human rights and counter terrorism, Martin Scheinin, said it was clear from the debate that the issue had not been brushed away despite months of delay.

"I don't think the Human Rights Council can ignore the need for inquiries at domestic level, that will necessarily be part of the package," he told journalists.

The experts noted a shift in attitude in Europe and the US government of President Barack Obama, even though domestic political battles had held up progress since the announced closure of secret CIA prisons.

However there was little promise of action from the United States and other major Western powers as well as countries like Iraq, Egypt, Morocco, Jordan, Syria and Djibouti.

UN expert: CIA drones claim 'licence to kill' with impunity

A UN human rights expert on Wednesday urged the United States to sideline the CIA from targeted killings using drones, warning that the practice amounted to "a licence to kill without accountability".

In a report to the UN Human Rights Council, Philip Alston, the special rapporteur on extrajudicial executions, warned that the "prolific" US use of targeted killings, mainly by unmanned aircraft, was setting a damaging example that other countries would follow.

"I’m particularly concerned that the United States seems oblivious to this fact when it asserts an ever-expanding entitlement for itself to target individuals across the globe," he told the 47-member council.

"But this strongly asserted but ill-defined licence to kill without accountability is not an entitlement which the United States or other states can have without doing grave damage to the rules designed to protect the right to life and prevent extrajudicial executions."

Alston's study on targeted killings sharply criticised the legal arguments invoked to justify them, their civilian toll and the involvement of the Central Intelligence Agency (CIA).

"Intelligence agencies, which by definition are determined to remain unaccountable except to their own paymasters, have no place in running programmes that kill people in other countries," Alston told the rights council.

Countries had to demonstrate that they were complying with rules limiting killings of targeted individuals to those directly involved in fighting, he underlined.

"The clearest challenge to this principle today comes from the programme operated by the US Central Intelligence Agency in which targeted killings are carried out from unmanned aerial vehicles or drones," Alston said.

He warned that hundreds of people had been killed including innocent civilians yet the CIA criteria for targeted killings remained shrouded in official secrecy.

"In a situation in which there is no disclosure of who has been killed, for what reason, and whether innocent civilians have died, the legal principle of international accountability is, by definition, comprehensively violated," he added.