Updated

The United States should open its detention centers at Guantanamo Bay, Cuba (search), and elsewhere to human rights investigators if it wants to dispute allegations of abuse, the head of Amnesty International (search) said in Tokyo on Thursday.

The group released a report last week comparing the camps to Soviet-era gulags, and urged Washington to close down Guantanamo Bay, where some 540 men accused of links to Afghanistan's ousted Taliban and the Al Qaeda (search) terror network are held.

President Bush dismissed the comparison to gulags as "absurd." But Irene Khan (search), secretary-general of the London-based human rights group, challenged Washington to prove its case by opening the camps to outside scrutiny.

"Our answer is very simple ... open up the detention centers, allow us and others to visit them," she told reporters. "Transparency is the best antidote to misinformation or incorrect facts."

Khan also defended the organization's choice of the word "gulag."

"We wanted to send a strong message that ... [the detention centers] are actually undermining human rights in a very dramatic way," she said.

There has been widespread criticism of the Guantanamo Bay operation, which began in January 2002 with the arrival of prisoners captured on the battlefield in Afghanistan.

Khan also criticized Japan's death penalty and urged the country to review the system. Japan and the United States are the only developed countries that still employ the death penalty.