ISLAMABAD - When Ahmed Rabbani ran out of paint to satisfy his artistic yearnings during 20 years of incarceration at Guantanamo Bay, he turned to whatever came to hand -- dirt, coffee grinds and even spices such as turmeric from the prison canteen. "Through painting, I would feel myself outside Guantanamo," the 53-year-old Pakistani said this week at an exhibition of his work in the port city of Karachi. "Painting was everything for me there."

Rabbani was detained by Pakistan authorities in September 2002 and handed over to the US Central Intelligence Agency for a bounty of $5,000. He was "sold" on the basis he was a notorious militant known as Hassan Ghul, but Rabbani always insisted it was a case of mistaken identity. He was also accused of recruiting his older brother Muhammed into extremist circles.

Both were never charged or faced trial during two decades in detention, and they were only released in February this year. Born in Mecca, Saudi Arabia, where his parents worked, Rabbani moved back to Karachi as a teen and was a taxi driver at the time of his detention. Fluent in Arabic, he specialised in guiding visitors from the Middle East -- a factor which contributed to him being misidentified.

While imprisoned in Guantanamo Bay, painting became an obsession for Rabbani, although years spent on hunger strike meant he was often too frail to even hold a brush. In "The Unforgotten Moon: Liberating Art from Guantanamo Bay", around two dozen pieces Rabbani was allowed to take from prison are on display -- alongside works by local artists who have "re-imagined" paintings that were confiscated.