Human rights group Amnesty defended its description of Guantanamo prison as a “gulag” Thursday and urged the United States to allow independent investigations of allegations of torture at its detention centers for terrorism suspects.

A verbal feud between Amnesty International and Washington has escalated since Amnesty last week compared the prison at the U.S. naval base at Guantanamo Bay, Cuba, to the brutal Soviet system of forced labor camps where millions of prisoners died.

President Bush dismissed as “absurd” the Amnesty report, which also said the United States was responsible for an upsurge in global human rights violations, and Defense Secretary Donald Rumsfeld called the description “reprehensible.”

“The administration’s response has been that our report is absurd, that our allegations have no basis, and our answer is very simple: if that is so, open up these detention centers, allow us and others to visit them,” Amnesty International Secretary General Irene Zubaida Khan told a news conference.

“Transparency is the best antidote to misinformation and incorrect facts,” said Khan, who is here to meet with Japanese officials.

The United States holds about 520 men at Guantanamo, where they are denied rights accorded under international law to prisoners of war.

Many have been held without charge for more than three years.

Khan rejected a suggestion that Amnesty’s use of the emotive term “gulag” had turned the debate into one over semantics, and distracted attention from the situation in the detention centers.

“What we wanted to do was to send a strong message that … this sort of network of detention centers that has been created as part of this war on terrorism is actually undermining human rights in a dramatic way which can only evoke some of the worst features of human rights scandals of the past,” she said.

“I don’t think people have got off the hook yet.”

Khan also said Japan’s bid for a permanent seat on the U.N. Security Council meant Tokyo should play a bigger role in the global fight for human rights and improve its own record at home.

Japan has stepped up its campaign for a permanent seat as part of an effort to boost its global clout in security affairs.

“Japan, by its strong bid to become a U.N. Security Council member, is subjecting itself to greater international scrutiny and that creates an imperative for change,” she said.

Khan urged Japan to abolish the death penalty, improve the treatment of prisoners, revise a strict stance toward refugees — only 15 refugees were accepted last year — and do more to prevent and protect victims of human trafficking.