Foul play?

Sarabjit Singh - an Indian citizen who was sentenced to death in Pakistan in 1991 on charges of spying and terrorism in Pakistan - was allegedly attacked on April 26 by two of his jail inmates, Amir Tanba and Mudasir, in Lahore's Kot Lakhpat prison.

The 49-year-old was immediately taken to a hospital in Lahore where he received medical treatment. He succumbed to his wounds on Thursday, the Lahore's Jinnah Hospital authorities confirmed.

The Indian government has strongly condemned Singh's murder and his death is likely to make the relations of the two South Asian rivals more acrimonious.

Right-wing groups in Pakistan had called on the government to execute Singh without delay.

Najam Sethi, the caretaker Chief Minister of the Punjab province of Pakistan, ordered a judicial inquiry into the incident.

Singh's body was taken to the Indian city of Amritsar after the Pakistani authorities handed it over to Indian diplomats.

"Dastardly act"

Singh's lawyer Owais Sheikh told DW from Lahore that his client had received death threats inside the prison. He said that he had already informed the jail authorities about it.

"Now the Pakistani authorities have to explain how anybody could attack Singh in a highly secured prison," he said, adding that it should also be investigated whether Singh had been attacked by people who did not want to see Indo-Pakistani ties improving.

Certain rights activists say the attack on Singh would not have been possible without the police help.

Pakistan's independent Human Rights Commission (HRCP) condemned the attack on Singh as a “dastardly act” and called on the government to punish the guilty. "The authorities have obviously failed to do their elementary duty of providing him (Singh) safety and security" it said in a statement.

The commission also said that the Indian and Pakistani authorities must ensure the safety of each other's prisoners languishing in jails.

"If the Pakistani government doesn’t reveal the real facts that led to Singh's death then I fear the Pakistani-Indian ties will deteriorate," Rashid Rahman, a Lahore-based journalist, told DW.

Singh's security was increased after the execution of Afzal Guru, who was convicted of involvement in the 2001 terror attack on the Indian parliament, earlier this year. The Pakistani authorities had expected a backlash from the Islamic groups for whom Guru was a "martyr."

A planned attack?

The Indian government said on Thursday Pakistan mistreated Singh in jail and that it did not cooperate with India after Singh was attacked.

It had requested that Pakistan release Singh on humanitarian grounds so that he could be treated in India or in any third country.

"The criminals responsible for the barbaric and murderous attack on Sarabjit Singh must be brought to justice," Indian Prime Minister Manmohan Singh said on Twitter. "Particularly regrettable that the Government of Pakistan did not heed the pleas to take a humanitarian view of this case."

Pakistan responded by saying it had provided the best treatment for Singh and was cooperating with Indian officials.

Singh's sister who flew to Pakistan after the attack told the media that her brother's security was compromised by Pakistani officials.

"If the attack was planned by the government itself, then there is no need for an inquiry. But if Sarabjit was attacked without the knowledge of the authorities, then an inquiry is definitely needed," she said.