Indian national Kashmir Singh was arrested in 1973 on espionage charges and sentenced to death by a court martial, Pakistan's Minister for Human Rights Ansar Burney said in a statement.

Singh, a father of three, had become 'mentally disabled' after spending the following 35 years in a cell under a secrecy act without ever seeing the sky or receiving a single visitor, Mr Burney said.

Mr Burney said he was tipped off about Singh by the Indian community in London and, after searching various Pakistani prisons, found him in the central jail in Lahore. where he was being kept under the Official Secrets Act.

'During all these years he had never received a single visitor or even seen the open sky, sun or moon,' the statement said.

'He, like other condemned prisoners, was locked in an overcrowded death cell for 23.5 hours a day, only allowed out for 30 minutes to stretch his legs.'

Mr Burney, a prominent rights activists who is part of a pre-election caretaker government, said President Pervez Musharraf had expressed 'shock and disbelief' and agreed to grant Singh his freedom in coming days.

'Kashmir Singh has gone through hell during the last 35 years. He has suffered more than enough for his alleged crime,' Mr Burney said.

He added that he was now trying to trace Singh's family in India.

Nuclear-armed Pakistan and India have fought three wars since their independence in 1947 but launched a slow-moving peace process in 2004.

They have recently held a series of prisoner exchanges, mainly of fishermen who strayed into each others' territorial waters and were detained. -- AFP