Murat Kurnaz, a 32-year-old German resident of Turkish descent, was seized in 2001 by CIA agents in Germany and sent to Afghanistan. He spent the next five years first at a detention camp in Kandahar and then in Guantanamo Bay, Cuba.
"There are still 150 people held there [in Cuba], and the number of torture prisons is not decreasing, it is actually on the rise," he said.
A probe into Kurnaz's alleged links to al-Qaeda yielded no solid evidence. By 2002, US and German intelligence officials concluded that accusations against him were groundless, but he was detained for several more years.
During a Congressional hearing in 2008, Kurnaz described having been waterboarded and electrocuted by CIA guards. He said three prisoners had died in Guantanamo, with the US Department of Defense claiming those were suicides, although inmates were watched round-the-clock.
Kurnaz said he had been glad to see CIA crimes dragged into the limelight in the recent report on the spy agency's "enhanced interrogation techniques."
"I'm glad it has been exposed. Perhaps [the revelation] will help lawyers build the case and bring those responsible to justice," Kurnaz said, adding he had little hope of ever seeing his torturers behind bars.
Kurnaz stressed that public pressure on US President Barack Obama was needed to make him deliver on the election promise to shut down Guantanamo, which Obama made twice – in 2008 and 2012 – while vying for the White House. Kurnaz said the president had already been slammed over his failure to deliver, but it was not enough to see the prison closed.
According to the former inmate, America's unchecked brutality and a string of military operations in the Middle East under President George W. Bush was the main reason behind the Islamic State (IS) insurgency.
"It [IS] is the result of the US policy. Had they never started the Iraq War and hanged Saddam Hussein, the IS would not have come [to Iraq]. I'm 99-percent sure of that. But the wars were declared, and now people are seeking revenge," he claimed.
The Islamic State, a Sunni terrorist group active in Syria and Iraq, has been fighting the Syrian government since 2012 and became part of Iraqi insurgency after the US invasion of Iraq in 2003. In June, the group declared a caliphate in the territories it occupied and rallied thousands of Muslims to its cause with the help of social media.