People gather at Nirankari Bhawan in Adliwal village near Amritsar. (PTI photo)

CHANDIGARH: Punjab chief minister Amarinder Singh on Sunday suspected Pakistan's ISI-backed Khalistani or Kashmiri terrorists' role in the Amritsar terror attack that killed three persons and injured twenty others. Amarinder also vowed that he would not let the "forces of terror" destroy the state's "hard-earned peace".

"The possibility of involvement of ISI-backed Khalistani or Kashmiri terror groups could not be ruled out (in the Amritsar terror attack)," said Amarinder Singh in an official statement, adding the forensic teams have been rushed to the spot and "all angles were being investigated".

The chief minister said his government was "on the top of things" and would "get to the bottom of the incident" soon and ensure that the culprits are nabbed and brought to book.

"Nobody will be allowed to get away with trying to disturb the peace and harmony of the state," he said.

Three persons were killed and at least twenty others were injured when two motorcycle-borne miscreants hurled a grenade at a religious congregation of over 200 devotees inside a Nirankari Bhawan at Adliwal village near Amritsar's Rajasansi area Sunday, the police said earlier.

In his statement, the chief minister said the preliminary investigations have revealed that two men - one of them with a flowing beard and both with their faces covered - forced their entry into the hall, brandishing a pistol.

They detained the sewadar, lobbed the grenade into the prayer room and fled on a motorcycle on which they had come, he added.

A small crater was formed by the impact of the explosion and was being examined by the forensic team, Amarinder Singh said, adding that the safety valve of the grenade too has been found and was being examined.

Soon after the attack, the chief minister reviewed the law and order situation in the state and and asked the state home secretary, Punjab police chief and director generals, law & order and intelligence, to rush to Rajasansi in Amritsar to supervise the ongoing probe into the grenade attack, an official spokesman said here.

Forensic teams too have been rushed to the spot and all angles were being investigated, said the chief minister.

Strongly condemning the grenade attack after reviewing law and order in the state, Amarinder Singh vowed that he will not let the "forces of terror" destroy the hard-earned peace in the state.

While making an appeal to the people "not to panic and remain calm," the chief minister tweeted, "We will not let the forces of terror destroy our hard-earned peace."

"I appeal to the people of Punjab to maintain peace in the wake of Amritsar bomb blast. I urge them not to panic and remain calm," he added.

Amarinder Singh's tweet followed soon after Punjab police chief Suresh Arora told PTI that the incident "appears to have a terror angle... we will take it as a terrorist act."

In his statement, the chief minister added that police teams have been rushed to raid suspected hideouts of the assailants and multiple teams are investigating various angles to crack the case.

The chief minister also directed police to immediately beef up the security at all sensitive places, including all Nirankari Bhawans, in the wake of the grenade attack - the first such indiscriminate act against innocent people in recent past.

Punjab had been severely hit by pro-Khalistan militancy in the 1980s and early 1990s, but it faced few terror attacks in recent years, barring the one in Pathankot over two years back.

Though the state had been hit by a series of targeted attacks since 2015/2016, this was the first attempt, in a long time, aimed at disturbing the peace in the state through indiscriminate killings, said the chief minister.

This strengthened the belief that Pakistan was continuing with its nefarious activities to disturb peace in the state, he added.

Amarinder Singh said 15 terror modules were busted in the past 18 months, with indications of Kashmiri terror links too in some instances as evidenced in the arrest of Kashmiri students from Jalandhar and in a case of grenade blast at Maqsudan police station.

Punjab DGP Arora had earlier told PTI the grenade attack on the religious congregation on outskirts of Amritsar city appeared to be a "terrorist act".

"It (this incident) appears to have a terror angle, because it is against a group (of people) and not against any individual. There is no reason to throw a hand grenade on a group of people, so we will take it as a terrorist act. Till proven otherwise, prima facie we will take it as that," he had said.

Punjab had been on alert following an input saying that a group of six to seven JeM terrorists were in the state, possibly in Ferozepur area.

The state had been put on alert after four persons snatched a SUV from its driver at gunpoint near Madhopur in Pathankot district last week.

