Ghulam Ahmad Dar (L) and his son Adil Ahmad Dar, who carried out the suicide attack in Pulwama on Feb 14.

A suicide bomber who killed 44 paramilitary policemen in Kashmir joined a militant group after having been beaten by troops three years ago, his parents told Reuters on Friday.

Pakistan-based Islamist militant group Jaish-e-Mohammad (JeM) has claimed responsibility for Thursday's car bomb attack on a security convoy, the worst in decades of insurgency in Jammu and Kashmir, India's only Muslim majority state. It comes months before the general election.

Adil Ahmad Dar, 20, from the village of Lethipora* in Kashmir, rammed a car full of explosives into the convoy, escalating tension between the nuclear-armed neighbours, which both claim the rugged Himalayan region.

"We are in pain in the same way the families of the soldiers are," said farmer Ghulam Hassan Dar, adding that his son had been radicalised after police stopped him and his friends on the way home from school in 2016.

"They were stopped by the troops and beaten up and harassed," Dar said, adding that the students were accused of stone-pelting. "Since then, he wanted to join the militants."

A video released by the militant group after the attack showed his son, dressed in military fatigues and carrying an automatic rifle, detailing his plan to carry out the bombing.

His mother, Fahmeeda, corroborated her husband's account.

"He was beaten by Indian troops a few years back when he was returning from school," she said. "This led to anger in him against Indian troops."

Both parents said they were unaware of their son's plan to attack the convoy.

Dar did not return home from his work as a labourer on March 19 last year, Fahmeeda added. "We searched for him for three months," she said.

"Finally we gave up efforts to bring him back home."

Reuters could not independently verify the two accounts. A spokesman for India's home ministry did not immediately respond to a request for comment.

Anger over the attack is growing in India, which accuses Pakistan of backing separatist militants in Kashmir. Pakistan denies that, saying it offers only political support to the region's suppressed Muslim people.

Jaish, one of the most deadly groups operating in Kashmir, has been designated a terror group by the United Nations since 2001.

Ghulam Hassan Dar said he blamed politicians for his son's death.

"They should have resolved the issue through dialogue," he said, referring to the conflict over Kashmir.

"It is they who are responsible for driving these youth into militancy. The sons of the common man die here, whether they are Indian troops or our sons."

* Editor's note: While Reuters says Adil Ahmad Dar is from Lethipora, India Today reporters have confirmed that he was from Gundibagh, Kakapora, about 10 km from Lethipura.