Amnesty International executive director William Schulz criticized the administration of US President George W. Bush for holding alleged battlefield combatants in "indefinite incommunicado detention" without access to lawyers in an interview with Fox News Sunday.

Schulz was pressed to substantiate Amnesty's claim in a May 25 report that the US prison camp at the Guantanamo Bay, Cuba naval base -- where hundreds of foreign terror suspects are being held indefinitely -- represents the "gulag of our times."

The gulag claim, referring to the notorious prison camp system of the Soviet Union, has drawn withering criticism from the US president, who called it "absurd." Vice President Richard Cheney and Defense Secretary Donald Rumsfeld have also slammed the rights group's claim.

Russian 1970 Nobel Prize winner Aleksandr Solzhenitsyn described the Soviet prison camp system in his best-selling book "The Gulag Archipelago."

Schulz said the gulag reference was not "an exact or a literal analogy."

"But there are some similarities. The United States is maintaining an archipelago of prisons around the world, many of them secret prisons into which people are being literally disappeared -- held in indefinite incommunicado detention without access to lawyers," Schulz told Fox.

Asked how AI could compare the detentions of millions of Soviet citizens in the gulag system to purported anti-US combatants captured on the battlefield, Schulz said some of those held in Guantanamo "happened to be in the wrong place at the wrong time.

"We do know that at least some of the 200 some prisoners who have been released from Guantanamo Bay have made pretty persuasive cases that they were imprisoned there, not because they were involved in military conflict but simply because they were enemies of the Northern Alliance," he said.

Schulz called for an official probe into the alleged rights abuses at US detention centers around the globe.

Amnesty refers in the May 25 report to Rumsfeld and US Attorney General Alberto Gonzales as alleged "torture architects."

The United States "should be the one that should investigate those who are alleged at least to be architects of torture, not just the foot soldiers who may have inflicted the torture directly, but those who authorized it or encouraged it or provided rationales for it," Schulz said.

According to Amnesty, Rumsfeld provided "the exact rules, 27 of them in fact, for interrogations, some of which do constitute torture or cruel, inhumane treatment," Schulz said.

The Guantanamo Bay camp and US detention practices have been the subject of renewed debate in recent weeks, sparked by a Newsweek magazine report -- since retracted -- that Guantanamo interrogators flushed a Koran in a toilet to rattle Muslim prisoners.

Amnesty is not the only rights group to have called on Washington to investigate alleged abuses at the camp -- Schulz pointed to released FBI documents that also raised concerns about Guantanamo interrogations.

US officials insist such concerns are unfounded, and that the "war on terror" detainees are treated as humanely as possible.

US soldiers have been tried and punished for abusing detainees -- notably at Iraq's Abu Ghraib prison, where at least one captive died -- but US officials say those are isolated incidents.

The furor sparked by Amnesty's claims shows no signs of abating.

The New York Times said Sunday that the Guantanamo Bay prison should be closed down, saying it had become "a national shame" and a "propaganda gift to America's enemies."

"What makes Amnesty's gulag metaphor apt is that Guantanamo is merely one of a chain of shadowy detention camps that also includes Abu Ghraib in Iraq, the military prison at Bagram Air Base in Afghanistan and other, secret locations run by the intelligence agencies," the Times said.

The Washington Post, whose editorial page has been more critical of Amnesty's gulag claim, reported Sunday -- citing Schulz -- that Amnesty's donations have quintupled and new memberships have doubled in the past week since it released its report.