Murat Kurnaz, 24, who was released in August because of lack of evidence he was involved in terrorist activities, said he endured "many types of torture -- from electric shocks to having one's head submerged in water, (subjection to) hunger and thirst, or being shackled and suspended."
A burly man with long reddish hair and a thick beard stretching down to his belly, Kurnaz spoke, betraying no emotion, to Turkey's CNN Turk television from his home in Bremen, northern Germany, in an interview aired here late Monday.
"They tell you 'you are from al Qaeda' and when you say 'no' they give the (electric) current to your feet.... As you keep saying 'no' this goes on for two or three hours," he said, adding he had several times lost consciousness.
He claimed he was once shackled to a ceiling for "four or five days".
"They take you down in the mornings when a doctor comes to see whether you can endure more," he said. "They let you sit when the interrogator comes.... They take you down about three times a day so you do not die."
Kurnaz also alleged prisoners were locked up in cells into which frigid or hot air was pumped.
"I saw several people die," he said. "Sometimes I thought I could no longer stand it and would also die."
He said he was once left without food for 20 days and spoke of psychological abuse, including "religious insults" such as the Holy Quran being kicked on the ground.
A Turkish citizen with permanent residency in Germany, Kurnaz was arrested in Pakistan after the September 11, 2001 attacks and turned over to US forces, who took him to a prison in the Afghan city of Kandahar before transferring him to Guantanamo in 2002.
He says he went to Pakistan to visit holy places and take religious courses.
German prosecutors have also dropped a long-running probe into Kurnaz on the grounds they failed to find any firm proof he belonged to a terrorist group.
Kurnaz has insisted throughout he was innocent, and on his return to Germany accused the government of former chancellor Gerhard Schroeder of colluding with the US forces.
Around 450 prisoners are being held at Guantanamo Bay -- some for years -- without charges being brought. Human rights lawyers have brought suits on behalf of the detainees, many of them picked up as suspected al Qaeda or Taliban fighters from Afghanistan.

Copyright AFP (Agence France-Presse), 2006