Detainees at the Guantanamo Bay detention camp say they were subjected to unknown drugs experimentations intended to coerce confessions.

Adel al-Nusairi, a former Saudi policeman captured by US forces in Afghanistan in 2002, describes his confessions after the shot as 'made-up' adding that he was unable to learn what drugs were injected before interrogations.

"I was completely gone," said Nusairi, now free in Saudi Arabia. "I said, 'Let me go. I want to go to sleep. If it takes saying I'm a member of al-Qaeda, I will'."

According to court documents, at least two dozen other former and current detainees at Guantanamo maintain they were given drugs or witnessed other inmates being drugged.

The Defense Department and the CIA, responsible for detaining terrorism suspects, however, denied using drugs as an enhancement for interrogations, and described such claims as either 'fabrications' or 'mistaken interpretations of routine medical treatment'.

This is while a memo by the then-Justice Department explicitly condoned the use of 'mind-altering substances' on prisoners as long as they did not inflict "profound" psychological damage.