Indian activists pose with pictures of late Sarabjit Singh. (DIBYANGSHU SARKAR/AFP/Getty Images) Indian activists pose with pictures of  Sarabjit Singh. (Dibyangshu Sarkar/AFP/Getty Images)

NEW DELHI – Perhaps the most famous Indian convict on death row in a Pakistani prison, Sarabjit Singh, succumbed to injuries from a fatal attack on him by fellow inmates on Thursday.

His death has soured the roller-coaster relations between India and Pakistan and stoked fresh tension, especially at a time when governments on both sides are weak.

After waiting for over two decades on death row, Singh’s case has been championed by human rights activists, lawyers and peace activists in both India and Pakistan, who advocated for his release on humanitarian grounds. Many spoke of his release as an important confidence-building measure needed to foster peace between the two nations.

His death risks increasing suspicion and hostility between India and Pakistan.

Singh, an Indian farmer from the border province of Punjab, was arrested by Pakistani authorities in 1991. He was convicted of spying on Pakistan and of involvement in bomb explosions that killed 14 people. Singh’s family here in India has said that the arrest was a case of mistaken identity. He was innocent, they said, and had accidentally strayed across the border while drunk.

Now, some Indians are accusing Pakistani authorities of foul play. His death has also precipitated a diplomatic crisis and a domestic challenge for India’s already beleaguered government, headed by Prime Minister Manmohan Singh.

“Death to Pakistan” was one slogan chanted by some lawmakers in parliament. Both Houses passed a resolution to condemn the “inhuman treatment” that the prisoner was subjected to.

“My brother was murdered in jail, Pakistan is dishonest,” said Dalbir Kaur, Singh’s sister. “It is my misfortune that I could not bring my brother back home alive. Had Indian governments tried harder, he would not have been martyred today.”

A Pakistani foreign office statement said that Sarabjit Singh was hospitalized because of injuries sustained “during a scuffle with fellow inmates” and added that despite being provided “the best treatment,” had died after a cardiac arrest.

Prime Minister Manmohan Singh demanded that the “criminals responsible for the barbaric and murderous attack on him must be brought to justice.”

“Today, Pakistan has shown its real face once again,” said India’s parliamentary affairs minister Kamal Nath.

The opposition Bharatiya Janata Party demanded that New Delhi immediately scale down diplomatic relations with Islamabad.

But many officials had  warned that Singh’s life might be threatened, especially after India hanged Ajmal Amir Kasab, a Pakistani citizen and the lone surviving man convicted of carrying out the deadly Mumbai attacks in 2008.

Most of the anger in India was aimed at the Indian government. Television news channel Times Now asked whether India’s “over-indulgent foreign policy allowed Pakistan to take India for granted.”