WASHINGTON -- An Afghan prisoner who died this week at Guantánamo was found hanging by a bed sheet in a prison camp recreation yard and apparently hanged himself, a military spokeswoman said Thursday.

Inayatullah, 37, was one of the last captives brought to the controversial camps in southeast Cuba by the Bush administration. He arrived in September 2007, and was described as an Al Qaeda emir in Iran who planned and directed the group’s terror operations.

His lawyer, Miami public defender Paul Raskind, countered that the man who died was never known as Inayatullah anywhere but in Guantánamo, never had a role in Al Qaeda and was in fact named Hajji Nassim and ran a cellphone shop in Iran near the Afghan border.

Rashkind also acknowledged that his client had a history of psychological problems that the military recognized at Guantánamo. “I have no doubt it was a suicide,” he said by telephone while traveling in St. Louis.

The Afghan’s mental health problems became so profound last year that Rashkind arranged to bring a civilian psychiatrist to the base to work with the man.

“This is really a sad mental health case ... starting from childhood,” he said. At Guantánamo, “they treated him pretty humanely, I’d have to say.”

Legal sources familiar with the case added that the Afghan had spent long stretches in the psychiatric ward at Guantánamo and had previous episodes where he had tried to harm himself.

Army Lt. Col. Tanya Bradsher, a Pentagon spokeswoman, would not say in which of the camps the captive was found dead of “an apparent suicide.” But she did say he was discovered early Wednesday morning “hanging from his neck by what appears to be bed linen.”

An autopsy was performed and one of Guantanamo’s shortest held captive would be repatriated to Afghanistan, Bradsher said, bringing the detention center’s captive census to 171.

Military officials would not say what led them to conclude the Afghan hanged himself. Moreover, the detention center’s spokeswoman, Navy Cmdr. Tamsen Reese said only that the death was “under investigation” when asked how it was possible that a captive could succeed in killing himself at a facility that boasts it has guards around the clock monitoring each detainee at all times, and describes itself as one of the most heavily scrutinized prison facilities in the world.

The military also would not say whether he was discovered hanging in the yard before dawn or after, or whether the captives had already conducted their first morning prayers.

Both the American Civil Liberties Union and Amnesty International called for independent civilian investigations of the death.

The Afghan became the sixth captive to die of what U.S. military officials declared an apparent suicide in the history of the camps. Two other Guantánamo captives died during the nine-year history of the camp of what the Pentagon said were natural causes.

In February, the military said Awal Gul, 48, an Afghan slated for indefinite detention as a one-time Taliban official, collapsed and died of an apparent heart attack after working out on an exercise machine in a Camp 6 recreation yard.

The Pentagon’s Southern Command outpost in Miami first disclosed the death of Inayatullah, who went by the one name, on Wednesday evening in a short news release. Southcom said guards discovered the man dead, and summoned health personnel who administered “extensive lifesaving measures” could not revive him. He was pronounced dead by a physician.