Indian death row convict Sarabjit Singh's sister Dalbir Kaur plans to return to India to seek advice on his treatment in the wake of unconfirmed reports that doctors had declared him brain dead.

Sarabjit's lawyer Awais Sheikh on Tuesday said Dalbir Kaur had informed him a short while ago of her intention to return to India.

It was not immediately clear whether Sarabjit's wife and two daughters would also return to India, he said.

"There are unconfirmed reports that doctors have declared Sarabjit brain dead and Dalbir Kaur's return could be linked to that," Sheikh said on phone from Lahore.

"Dalbir Kaur was asked by the local media if she had agreed to take Sarabjit off ventilator support and she said no," he said.

Sarabjit's family members had arrived in Pakistan on Sunday, two days after the 49-year-old prisoner sustained severe injuries, including a fractured skull, during a brutal assault by prisoners in Lahore's Kot Lakhpat Jail.

He has been in a deep coma in an intensive care unit of the Jinnah Hospital and doctors have said his chances of survival are slim.

Sarabjit was convicted by a Pakistani court of alleged involvement in a string of bombings in Punjab that killed 14 people in 1990.

Sarabjit's family says he is the victim of mistaken identity and had inadvertently strayed across the border in an inebriated state.