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 regime or the al-Qaida 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," 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 that Haiti promoted human rights abusers.

On Canada, the report highlighted reports that "indigenous women and girls continued to suffer a disproportionately high incidence of violence." It said Canadian authorities failed to "reduce the marginalization of these women and ensure that police understand and are accountable to indigenous peoples."

It also mentioned "continuing concerns about the use by police of Taser guns," saying that six men have died in separate incidents in Canada after they were subdued with Tasers, which use electric shocks to stun people.

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 UN 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 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 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 prisoner of wars 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 U.S. Defence Department 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.

The report also takes aim at recent abuse allegations that have surfaced in FBI documents as well as prisoner testimonies. The Red Cross said last week it had told U.S. authorities of detainee allegations that Qur'ans had been desecrated.

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 two million have fled their homes to escape fighting among rebels, militias and government troops.

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.