An Indian man sentenced to death 22 years ago on espionage charges by a Pakistani court died on Thursday, after being brutally attacked in a Lahore jail by fellow inmates, news agencies reported citing medical officials and his lawyer.

Sarabjit Singh, who was convicted for spying and for his role in bomb attacks that killed 14 people in Pakistan in 1990, was attacked with bricks by prisoners in Lahore's Kot Lakhpat jail on Friday.

Mahmood Shaukat, the head of a medical board that was supervising Sarabjit's treatment at Lahore's Jinnah Hospital, told the Press Trust of India (PTI) news agency, he received a call from the doctor on duty at 01:00 a.m. on Thursday morning (20:00 GMT on Wednesday) informing him of the death.

Another doctor, who was part of the team treating Singh told PTI he died of cardiac arrest, adding that doctors made several unsuccessful attempts to resuscitate him.

Officials of the Indian high commission in Islamabad said they had been informed by officials of the Jinnah Hospital about Singh's death.

Singh's lawyer Owais Sheikh confirmed his death to the AFP news agency and said his body had been moved to the hospital mortuary.

A senior doctor at the Jinnah hospital told AFP that arrangements were underway for an autopsy, although the PTI reported citing supervising head Shaukat that authorities were yet to decide on conducting an autopsy on Singh’s body.

There was no official statement from the Pakistani government announcing the death, an issue that risks straining the ties between New Delhi and Islamabad.

India had appealed for Singh to be released or transferred to India over concerns about his treatment following his attack. Singh, 49, had been lying in a coma after he suffered multiple serious injuries when six prisoners attacked him on April 26.

Two inmates were charged with attempted murder and two officials suspended.

Four members of Singh's family — his wife, two daughters and his sister — had returned to India on Wednesday morning after spending three days with him in Lahore. His family insisted he was a victim of mistaken identity after inadvertently straying across the border while drunk.

Singh, a resident of Amritsar in northern Indian state of Punjab, was arrested near the Kasur border in August 1990 on charges of illegally crossing into Pakistan from India. Police in Pakistan later charged him for being involved in a series of bombings in Lahore and Faisalabad that killed 14 people.

In a tweet, Indian Prime Minister Manmohan Singh's office wrote: “Particularly regrettable that the Govt of Pakistan did not heed the pleas... to take a humanitarian view of this case.”

Singh’s lawyer said his client had received threats after India executed in February Kashmiri Muslim Afzal Guru, who was sentenced to death more than eight years ago for his role in the attack on Indian Parliament in 2001.

Guru’s hanging followed that of Ajmal Kasab, a Pakistani who was the sole surviving perpetrator of the 2008 Mumbai attacks.

Sarabjit Singh’s family has demanded that his body be cremated with full state honors, and he be declared a “martyr,” the PTI reported.