Despite President George W. Bush's staunch defence of US interrogation methods as "within the law," the White House remained under attack for not distancing itself from practices some critics repudiate as torture.

The president on Monday seemed to take a firm stance against the abusive treatment of terror suspects, telling a press conference in Panama City "We do not torture," as he wrapped up a five-day swing through Latin America.

But Bush's assertion has been met with scepticism from some critics, who point to a Washington Post report this week that the Central Intelligence Agency (CIA) is interrogating captured al-Qaeda operatives at secret prisons in Eastern Europe, Afghanistan, Thailand and elsewhere. The White House would neither confirm or deny the existence of the facilities, which have been dubbed "black sites," but the CIA has asked the Justice Department to investigate the leak of the classified information to the Post.

The disclosure has once again put the White House on the defensive in the heated national debate over torture, which comes some 19 months after the publication of explosive pictures showing the mistreatment of detainees at Iraq's Abu Ghraib prison.

On Wednesday, US Attorney General Alberto Gonzales insisted again that US laws on torture are sufficient, telling AFP: "There already exist domestic and international legal prohibitions binding upon the United States in regards to torture."