GENEVA - Washington has, for the first time, acknowledged to the United Nations that prisoners have been tortured at US detention centres in Guantanamo Bay, as well as Afghanistan and Iraq, a UN source said.

The acknowledgment was made in a report submitted to the UN Committee against Torture, said a member of the ten-person panel, speaking on on condition of anonymity.

'They are no longer trying to duck this and have respected their obligation to inform the UN,' the Committee member said.

'They they will have to explain themselves (to the Committee). Nothing should be kept in the dark,' he said.

UN sources said this is the first time the world body has received such a frank statement on torture from US authorities.

The Committee, which monitors respect for the Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, is gathering information from the US ahead of hearings in May 2006.

Signatories of the convention are expected to submit to scrutiny of their implementation of the 1984 convention and to provide information to the Committee.

The document from Washington will not be formally made public until the hearings.