London ? Amnesty International castigated the U.S. prison camp in Guantanamo Bay 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 regime or the al-Qaida terror network. Some have been jailed for more than three years without charge.

The influential human-rights monitoring group also demanded an independent investigation of torture and abuse of prisoners there and at detention facilities in Iraq and Afghanistan.

White House spokesman Scott McClellan said Amnesty’s complaints were “ridiculous and unsupported by the facts.”

In its annual report, Amnesty accused governments around the world of abandoning human rights protections. 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.

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 Qurans, the holy book of Muslims, had been desecrated.

Declassified FBI records released Wednesday showed that prisoners at Guantanamo Bay told U.S. interrogators as early as April 2002 that U.S. military guards abused them and desecrated the Quran.