Amnesty International (search) castigated the U.S. prison camp in Guantanamo Bay (search) as a failure Wednesday, calling it "the gulag of our time" in the human rights group's harshest rebuke yet of American detention policies.

Amnesty urged Washington to shut down the prison at the U.S. Navy's base in Guantanamo Bay, Cuba, where some 540 men are held on suspicion of links to Afghanistan's ousted Taliban (search) regime or the Al Qaeda terror network. Some have been jailed for more than three years without charge.

White House spokesman Scott McClellan said Amnesty's complaints were "ridiculous and unsupported by the facts." He said allegations of prisoner mistreatment are investigated.

"We hold people accountable when there's abuse. We take steps to prevent it from happening again. And we do so in a very public way for the world to see that we lead by example and that we do have values that we hold very dearly and believe in," McClellan told reporters.

In its annual report, Amnesty accused governments around the world of abandoning human rights protections. It said Sudan failed to protect its people from one of the world's worst humanitarian crises and charged Haiti promoted human rights abusers.

But one of the biggest disappointments in the human rights arena was with the United States, Amnesty said, "after evidence came to light that the U.S. administration had sanctioned interrogation techniques that violated the U.N. Convention against Torture."

"Guantanamo has become the gulag of our time," Amnesty Secretary General Irene Khan said as the London-based group issued a 308-page annual report that accused the United States of shirking its responsibility to set the bar for human rights protections.

The use of the term gulag refers to the extensive system of prison camps in the former Soviet Union, many in remote regions of Siberia and specifically designed to hold political prisoners. The Soviets took over the system from the czarist government and expanded it after the 1917 Bolshevik Revolution. Untold thousands of prisoners of the so-called gulags died from hunger, cold, harsh treatment and overwork.

The prison camp at Guantanamo has been in the spotlight over the past year since the FBI cited cases of aggressive interrogation techniques and detainee mistreatment. The U.S. government has also been criticized for not charging or trying prisoners who are classified as enemy combatants, a vague distinction with fewer legal protections than prisoners of war get under the Geneva Conventions.

Some prisoners have challenged their detentions in U.S. courts but their cases are stalled by appeals filed by the U.S. government and subsequent arguments.

"Not a single case from some 500 men has reached the courts," Khan said.

In a statement, the Defense Department (search) said that "the detention of enemy combatants is not criminal in nature, but to prevent them from continuing to fight against the United States in the War on Terrorism."

It also said that it continued to evaluate whether detainees should be sent home and that review tribunals "provided an appropriate venue for detainees to meaningfully challenge their enemy combatant designation."

"This is an unprecedented level of process being provided to our enemies in a time of war," the statement said.

The Geneva-based International Committee of the Red Cross, which has also been critical of practices at Guantanamo, is the only independent group to have access to the detainees. Amnesty has been refused access to the prison, although it was allowed to watch pretrial hearings for 15 detainees who have been charged.

Amnesty has frequently criticized U.S. detention policies instituted after the Sept. 11 terror attacks, but its latest report takes a harsher tone. It accuses Washington of trying to "sanitize" abuse of detainees and failing to give prisoners legal recourse to challenge their detentions.

The report also takes aim at recent abuse allegations that have surfaced in FBI documents as well as prisoner testimonies, echoing concerns from the International Committee of the Red Cross.

The Red Cross said last week it had told U.S. authorities of detainee allegations that Korans had been desecrated. It also offered a rare public rebuke in late 2003, calling the prisoners' prolonged detentions "worrying."

Declassified FBI records released Wednesday showed that prisoners at Guantanamo Bay told U.S. interrogators as early as April 2002, just four months after the first detainees arrived from Afghanistan, that U.S. military guards abused them and desecrated the Koran.

Another detainee stated he had been beaten unconscious at Guantanamo Bay early in 2002, a period in which U.S. interrogators were pressing hard for information on Al Qaeda.

Amnesty singled out Sudan as one of the worst violators of human rights last year for the devastation caused by conflict in its Darfur region. At least 180,000 people have died -- many from hunger and disease -- and about 2 million have fled their homes to escape fighting among rebels, militias and government troops.

Sudan's government not only turned its back on its people, but the United Nations and African Union took too long to try to help those suffering in Darfur, Amnesty said.

Amnesty also criticized the African Union and the international community for not taking action on Zimbabwe, where President Robert Mugabe's party has been accused of rigging elections, repressing opponents and driving agriculture to the brink of collapse.

In Haiti, human rights violators who led the rebellion that ousted President Jean-Bertrand Aristide last year were able to retake key positions, while the government struggled to maintain control from armed groups, Amnesty said.

The group accused Israeli soldiers of operating outside international law by using torture, destroying property and obstructing medical assistance in the West Bank and Gaza. It also condemned the deliberate targeting of Israeli civilians by Palestinian militants.

In Asia, people were jailed indefinitely without trial in Malaysia and Singapore, religious minorities were persecuted in China and Vietnam and security forces committed extra-judicial killings in Nepal, Thailand and Indonesia, Amnesty said.