The U.S. military prolonged Omar Khadr's detention at its prison in Guantanamo Bay in part because the young Canadian continued "to provide valuable information" during interrogations, a secret 2004 document reveals.

Khadr coughed up details about purported al-Qaeda training camps, "key" al-Qaeda and Taliban militants, and "non-governmental organizations that he worked with in supporting al-Qaeda," the file says.

"Detainee has been generally co-operative and forthcoming," reads the memo, addressed to the head of the U.S. military's Southern Command, which includes the naval base and prison at Guantanamo Bay, Cuba.

The document was obtained by the whistleblower website WikiLeaks and released Sunday night. It lists the U.S. Defence Department's "reasons for continued detention" of Khadr, who was captured in Afghanistan in 2002, at age 15, following a firefight with American special forces.

Khadr pleaded guilty last October to throwing a grenade that killed a U.S. medic during the melee and to four other charges, including providing material support to terrorists.

One of the reasons the memo cites for keeping him at the Guantanamo prison is that he "never expressed any genuine remorse for the killing of that soldier." The U.S. said all along that he had confessed to the killing early in his detention, but Khadr's defence lawyers maintained that any confession was extracted, like some other prisoners' admissions, through torture.

The vast majority of the more than 700 captives who have spent time at Guantanamo Bay since 2001 were released without charge, sometimes into the custody of their home countries.

Leaked files

Khadr is one of 172 remaining Guantanamo detainees and the last Western citizen there. He will be eligible in the fall for transfer to a Canadian penitentiary to serve out the remaining seven years of his sentence.

His advocates have decried his continued detention, pointing out that international law requires child soldiers to be treated not as a hardened militants, but as victims in need of rehabilitation.

WikiLeaks began the release of 779 secret files on the Guantanamo Bay camp Sunday night. So far, most of the documents are prisoner assessments, but one divulges that Canada's spy service was duped by an al-Qaeda double agent .

The leak follows last year's release by the website of hundreds of thousands of classified documents from the U.S. invasion of Iraq, the war in Afghanistan and American diplomatic cables.

The files disclosed Sunday also reveal that another prisoner at Guantanamo was a journalist for Al-Jazeera who was held for six years, partly in order to be interrogated about the Mideast news network.