India has issued a fresh appeal to Pakistan to release on "humanitarian grounds" convicted Indian spy Sarabjit Singh who is currently in a coma at a hospital in Pakistan following a deadly attack on him by his fellow inmates in a jail last week.

"In view of the recent tragic events and present circumstances, we once again appeal to the government of Pakistan to take a sympathetic and humanitarian view of this case, and release Sarabjit Singh," a statement issued by the Indian External Affairs Ministry has said.

"Officials of the Indian High Commission are in touch with the medical authorities at Jinnah Hospital Lahore (where Singh has been admitted) and we'd like to consider the option of transferring Sarabjit Singh to India so that he can benefit from the best medical treatment available here," it added.

Singh, on death row for more than 21 years in Pakistan after being convicted of spying for India and involvement in a series of bomb blasts in 1990 in which 14 people were killed, was attacked by inmates armed with bricks in Lahore's Kot Lakhpat jail Friday.

His is battling for his life at Jinnah Hospital and his family members are in Lahore currently.

Indian Prime Minister Manmohan Singh has described as "very sad " the attack on Singh, which is perceived to be in retaliation against India's execution of Kashmiri terrorist Afzul Guru in February for his role in the 2001 Parliament attacks.