New Delhi, Apr 27 (IANS): Prime Minister Manmohan Singh Saturday said the murderous attack on Indian death row prisoner in Pakistan Sarabjit Singh was "very sad".

"Yes, it is very sad, some inmates attacked him in jail. I think that is a very sad development," Manmohan Singh told reporters on the sidelines of a function at Rashtrapati Bhawan here.

Sarabjit Singh was admitted to the intensive care unit (ICU) of Lahore's Jinnah Hospital after the murderous attack on him by fellow prisoners Friday afternoon. He reportedly suffered critical head injuries in the assault. He was attacked with bricks, sharp objects and plates.

The reason behind the assault was not immediately known. Doctors are battling to save his life, said an official of India's external affairs ministry.

The assault on Sarabjit Singh comes a few months after the death of Indian prisoner Chamel Singh in the same Kot Lakhpat Jail after he was allegedly assaulted by the jail staffers.

Sarabjit Singh has been on death row in Pakistan since 1990, after being convicted by Pakistani courts for bomb blasts in Lahore and Multan cities, which left 14 people dead. Sarabjit's family claims that he had inadvertently crossed into Pakistan in August 1990 in an inebriated state and was arrested there.

But police in Pakistan claimed Sarabjit Singh was involved in acts of terrorism.