AMRITSAR, India (AFP) - A Pakistani prisoner who was savagely beaten in an Indian jail in an apparent tit-for-tat assault died on Thursday, prompting Islamabad to demand an international probe into the "heinous" crime.

Doctors treating Sanaullah Ranjay at a government hospital in Chandigarh said the 52-year-old died of multiple organ failure after suffering severe head injuries in last week's attack at a prison in the northern city of Jammu.

The chief minister of Jammu and Kashmir, India's only Muslim majority state, said that an inquiry would identify those responsible for any lapses that led to the May 3 attack on Ranjay, calling it a "matter of deep regret".

But Pakistani officials said they would not be satisfied by an Indian inquiry into the "extra-judicial killing", calling instead for an international-level investigation.

Ranjay's death comes exactly a week after Sarabjit Singh, an Indian who was being held in Lahore's Kot Lakhpat prison after being convicted on espionage charges, died as a result of an assault by inmates.

In a statement, the hospital said Ranjay had been declared dead at around 7am.

"He had multiple organ failure due to severe head injury. The team of doctors headed by Prof YK Batra tried their best to revive him," it said.

One of his doctors told AFP on condition of anonymity that Ranjay had died after suffering kidney failure on Wednesday night.

A spokesman for the Pakistan High Commission said that the Indian government had been asked to immediately release and repatriate the body.

"We are in shock and deep grief over this barbaric act," the spokesman Manzoor Ali Memon told AFP.

"This is an extra-judicial killing of an innocent citizen of Pakistan right under the noses of the Indian jail authorities.

"We have demanded an inquiry of international level to find out the culprits and expose the connivance."

The Pakistani foreign ministry said that the "brutal" attack was "a matter of deep concern" to the government in Islamabad.

"We have conveyed our concern to the government of India in this regard and demanded that an investigation into the incident be held and perpetrators of this heinous crime be brought to justice," it said in a statement.

"The prime minister of Pakistan has also called upon the government of India to ensure the safety and security of all Pakistani prisoners in Indian jails," it added.

India's Home Minister Sushilkumar Shinde said the government would only respond to Pakistan's demand for an international probe once it receives a formal request from Islamabad.

Ranjay, seen with a flowing long beard and playing the bagpipes in one of the photos released by Jammu prison authorities, was serving a life term after being convicted for a 1994 bus bombing in the state that killed 10 people.

Jammu and Kashmir Chief Minister Omar Abdullah promised that those responsible for Ranjay's death would be held accountable.

"While the inquiry will fix responsibility for any dereliction of duty, the fact that this is happening at all is a matter of great regret," he wrote on Twitter.

The attack on Sanjay has fuelled tensions in Kashmir, the picturesque but violence-torn Himalayan region that is claimed by both countries.

Demonstrators took to the streets in Pakistan-administered Kashmir last weekend, with more than 200 people marching in the city of Muzaffarabad, calling for a "jihad" to force Indian troops out of Kashmir.

Nuclear-armed India and Pakistan, whose relations were hit by a border flare-up earlier this year, have fought two of their three wars over Kashmir.

New Delhi says 535 Indian prisoners, including 483 fishermen, are in Pakistani jails, while 272 Pakistani prisoners are behind bars in India.