The United States should close its prison at Guantanamo Bay, Cuba, and avoid using secret detention facilities in its war on terror, a U.N. panel report released Friday said.

In a report on U.S. adherence to the world body's anti-torture treaty, the U.N. Committee Against Torture said detainees should not be returned to any state where they could face a "real risk" of being tortured.

"The state party should cease to detain any person at Guantanamo Bay and close the detention facility," said the panel of 10 independent experts.

The committee said it was concerned that detainees were being held for protracted periods with insufficient legal safeguards and without judicial assessment of the justification for their detention.

The administration of President George W. Bush has been widely criticized for the open-ended detention of people captured in the war on terrorism at the camp that holds about 490 "enemy combatants."

But U.S. State Department legal adviser John B. Bellinger III, who led the U.S. delegation at the U.N. panel hearing earlier this month, said that the panel appeared not to have read a lot of the information Washington had supplied, or had ignored it.

"There are a number of both factual inaccuracies and legal misstatements about the law applicable to the United States," Bellinger told The Associated Press.

The committee was also concerned about allegations that the United States has established secret prisons, where the international Red Cross does not have access to the detainees. The report did not specifically say that such prisons existed, but stated the United States "should ensure that no one is detained in any secret detention facility under its de facto effective control."

Washington should also "investigate and disclose the existence of any such facilities and the authority under which they have been established and the manner in which detainees are treated."

The report also said the United States must eradicate all forms of torture committed by military or civilian personnel in Afghanistan, Iraq and other places of detention under its control and investigate allegations thoroughly, prosecuting any staff found guilty.

It pointed in particular to "any interrogation technique — including methods involving sexual humiliation, 'water boarding,' 'short shackling' and using dogs to induce fear."

Water boarding is a controversial technique in which a subject is made to think he is drowning. Short shackling involves shackling a detainee to a hook in the floor to limit movement.

The panel was also concerned that the United States was sending suspects, without judicial review, to states where they may be tortured, a process known as "extraordinary rendition."

Andreas Mavrommatis, a Cypriot rights expert who chaired the committee's review of the United States, said the report should not be blown out of proportion because overall the United States has "a very good record of human rights."

"Yes, we have identified certain" problems in the war on terror, Mavrommatis told reporters. "We are telling them we hope to have a dialogue, and we trust that they might take the necessary measures to improve."

The United States made its first appearance in six years before the U.N. Committee Against Torture earlier this month, addressing a series of issues ranging from Washington's interpretation of the absolute ban on torture to its interrogation methods in prisons such as Abu Ghraib, Iraq, and Guantanamo.

The panel said some techniques "have resulted in the death of some detainees during interrogation" and criticized vague U.S. guidelines that "have led to serious abuse of detainees."

But Bellinger said that the U.S. record had improved.

"There have been allegations of abuse which we have fully investigated and we have tightened our laws and our procedures, so we believe that we are already working very hard to address the areas of concern raised by the committee," he said.

Bellinger added that the United States was working "very hard" to address concerns about Guantanamo, but that critics had failed to come up with suggestions on what to do with the detainees.

"If you add in the recommendation in this report that Guantanamo ought to be closed but large numbers of people can't be sent back to certain countries, there's not really a very good solution," he said.

The panel asked the United States to report back within a year with its response to several of its concerns and recommendations.