Alleged 9/11 plotter held at Guantanamo illegally should be released immediately, says UN

His interrogation inspired scenes in the film 'Zero Dark Thirty'

The Pakistani citizen has been accused of helping plot the 9/11 attacks (AP)

A Pakistani man accused of helping plot the 9/11 attacks and being held at Guantanamo Bay, is being detained illegally and should be released immediately, a UN rights body has said.

The UN Working Group on Arbitrary Detention said there was no legal basis for holding of Ammar al Baluchi, who has been at the military-run jail on Cuba since 2006. It said the prisoner, whose torture and interrogation inspired scenes in the movie Zero Dark Thirty, should be released and paid compensation.

“Mr al Baluchi has been subject to prolonged detention on discriminatory grounds and has not been afforded equality of arms in terms of having adequate facilities for the preparation of his defence under the same conditions as the prosecution,” the group said in a report released in Geneva.

“He has been deprived of due process and the fair trial guarantees that would ordinarily apply within the judicial system of the United States.”

It said the prisoner, believed to be aged either 40 or 41, “should be released immediately and given an enforceable right to compensation and other reparations”.

Mr al Baluchi, said to be the cousin of alleged 9/11 mastermind Khalid Sheikh Mohammed, was captured by the Pakistani authorities in April 2003 and handed over the US. A US Senate Intelligence Committee report released in 2014 said he was taken to a notorious CIA black site known as the Salt Pit, near Kabul.

At the prison, he was subjected to torture that included being dunked in a bath filled with ice water, his head being held under water as he struggled to breathe, being hit repeatedly with a truncheon and his head being smashed into a wall.

The UN body said Mr al Baluchi should be provided with “appropriate physical and psychological rehabilitation” for the torture he suffered.

It added: “Widespread or systematic imprisonment or other severe deprivation of liberty in violation of the rules of international law may constitute crimes against humanity.”

Cmdr Sarah Higgins, a Department of Defence spokesperson, said in a statement: “The U.S. government has the legal authority to detain al Baluchi. Until we have time to analyse the basis of their claim, we will delay further comment.