New Delhi, May 2 (IANS): The death of Sarabjit Singh in a Lahore hospital days after a brutal attack on him in a prison was "put simply, the killing of our citizen while in the custody of Pakistan jail authorities", the external affairs ministry said Thursday.

In a statement, the ministry said India has asked Pakistan to "release the body of Sarabjit Singh so that he can be given a funeral in India and among his own people".

It said the "shocking attack" on Singh in Lahore's Kot Lakhpat jail April 26 "highlights the need for concerted action by Pakistan to safeguard Indians in Pakistani jails".

India has also demanded that Pakistan conduct a "thorough investigation" to identify those responsible for the attack on him and "ensure they are punished", the statement said.

"We express great anguish at the demise of Sarabjit Singh who succumbed to injuries after the brutal attack on him at Kot Lakhpat jail," it said.

"We share the pain and sorrow of Sarabjit Singh's family."

Sarabjit Singh suffered serious head injuries after the attack on him by prisoners at Kot Lakhpat jail April 26. He had been on ventilator support since then.

Sarabjit Singh had been on a death row in Pakistan since 1990 after being convicted by Pakistani courts for bomb blasts in Lahore and Multan, which left 14 people dead.