The report was denounced by the White House, reports CBS News correspondent David Martin and White House spokesman Scott McClellan rejected the call to shut the camp, saying the military treats all detainees humanely and "these are dangerous terrorists that we're talking about."
The panel's report, released Wednesday in Geneva and, said the United States must close the detention facility "without further delay" because it is effectively a torture camp where prisoners have no access to justice.
Annan told reporters he didn't necessarily agree with everything in the report, but he did support its opposition to people being held "in perpetuity" without being charged and prosecuted in a public court. This is "something that is common under every legal system," he said.
"I think sooner or later there will be a need to close the Guantanamo (camp), and I think it will be up to the government to decide, and hopefully to do it as soon as is possible," the secretary-general told reporters.
The 54-page report summarizing an investigation by five U.N. experts, accused the United States of practices that "amount to torture" and demanded detainees be allowed a fair trial or be freed. The panel, which had sought access to Guantanamo Bay since 2002, refused a U.S. offer for three experts to visit the camp in November after being told they could not interview detainees.
Annan said the report by a U.N.-appointed independent panel was not a U.N. report but one by individual experts. "So we should see it in that light," he said.
U.N. spokesman Stephane Dujarric said the report will be presented to the U.N. Commission of Human Rights, which appointed the panel, when it convenes on March 13 in Geneva.
"The Guantanamo report was an easy target for the Bush Administration to criticize because this is a case where the message may be right but the messenger lacks credibility," says CBS News Foreign Affairs Analyst Pamela Falk, who has been to the Guantanamo base twice. "The report was produced by the same U.N. Human Rights Commission that has been discredited by the Secretary General himself because some of its members have been the worst human rights violators, including Syria, Sudan, Cuba and Zimbabwe."
Manfred Nowak, the U.N. investigator for torture who was one of the panel's experts, told The Associated Press in Geneva that the detainees at Guantanamo "should be released or brought before an independent court."
"That should not be done in Guantanamo Bay, but before ordinary U.S. courts, or courts in their countries of origin or perhaps an international tribunal," he said.
The United States should allow "a full and independent investigation" at Guantanamo and also give the United Nations access to other detention centers, including secret ones, in Iraq, Afghanistan and elsewhere, Nowak said by telephone from his office in Vienna, Austria.
"We want to have all information about secret places of detention because whenever there is a secret place of detention, there is also a higher risk that people are subjected to torture," he said.
Martin reports Bush administration officials have taken to calling the war against terror "The Long War" and Guantanamo is likely to be in operation for as long as the war goes on — and likely to be a sore point with the rest of the world.
"These are the things that's creating the hatred and creating more terrorism around the world by the fact that we are such hypocrites," said James Bamford, Author of A Pretext for War. "We want the world, these places we invade, to be democratic and have democratic institutes. Yet when we capture people we won't do the same thing. We treat them as if Saddam Hussein had captured these people. Put them away, don't give them a trial, and throw away the key."
The issue of closing Guantanamo has come up before, Martin reports, but the answer has always been no, because closing it would only required opening another detention center someplace else.
The U.N. investigators said photographic evidence — corroborated by testimony of former prisoners — showed detainees shackled, chained and hooded. Prisoners were beaten, stripped and shaved if they resisted, they said.
The report's findings were based on interviews with former detainees, public documents, media reports, lawyers and questions answered by the U.S. government, which detailed the number of prisoners held but did not give their names or the status of charges against them.
Some of the interrogation techniques — particularly the use of dogs, exposure to extreme temperatures, sleep deprivation and prolonged isolation — caused extreme suffering, the report said.
"Such treatment amounts to torture, as it inflicts severe pain or suffering on the victims for the purpose of intimidation and/or punishment," the report said.
The International Committee of the Red Cross is the only independent monitoring body allowed to visit Guantanamo's detainees, but it reports its findings solely to U.S. authorities.
Legislators and journalists have been allowed in on guided tours but few are permitted to see interrogations.
Pentagon spokesman Bryan Whitman said the U.N. report "clearly suffers from their unwillingness to take us up on our offer to go down to Guantanamo to observe first-hand the operations."
McClellan, the White House spokesman, echoed Whitman, saying "it's a discredit to the U.N. when a team like this goes about rushing to report something when they haven't even looked into the facts. All they have done is look at the allegations."
Although his statement did not address specific allegations, the Pentagon has acknowledged 10 cases of abuse or mistreatment at Guantanamo, including a female interrogator climbing onto a detainee's lap and a detainee whose knees were bruised from being forced to kneel repeatedly.
In Strasbourg, France, the European Parliament condemned the treatment of prisoners at Guantanamo and renewed its calls for the detention center to be closed.
Human rights activists also supported the investigators' findings.
Amnesty International said the report was only the "tip of the iceberg."
"The United States also operates detention facilities at Bagram Airbase in Afghanistan, Abu Ghraib and elsewhere in Iraq and has been implicated in the use of secret detention facilities in other countries," an Amnesty statement said.
Many of the allegations in the report have been made before. But the document represented the first inquiry launched by the 53-nation U.N. Human Rights Commission.