Amarinder blamed Pakistan's Inter-Services Intelligence (ISI) agency and the Pakistan-based masterminds of the Khalistan Liberation Force (KLF) for the terror attack.

The arrested person has been identified as Bikramjit Singh, 26, a resident of Dhariwal village near Rajasansi area of Amritsar. he said. He was arrested early on Wednesday from near Loharka village in Amritsar district.

The second person involved in the attack, identified as Avtar Singh, is still absconding.

It was Avtar who threw the grenade at the Nirankari prayer meeting on Sunday, leaving three people dead and 15 others injured. Bikramjit had stood at the gate of the Nirankari bhawan premises, holding the gate attendants at gun-point.

The Chief Minister said the grenade used in the blast was Pakistan made, and added that the motorcycle used in the crime has also been recovered.

Amarinder said it was a "terror incident" and there was no religious link to it.

"Bikram, a KLF operative, has given significant information indicating that the grenade was provided to the assailants by one Happy in Pakistan," Amarinder said.

"Happy is suspected to be the Pakistan-based KLF chief...Harmeet Singh Happy @ Ph.D, who had earlier masterminded the conspiracy to carry out targeted killings of RSS/ Shiv Sena/ DSS leaders and workers (and a Christian Pastor) in Ludhiana and Jalandhar in 2016-2017, in active collaboration with Pakistani establishment and the ISI," he added.

The Chief Minister categorically ruled out any religious motivation behind the attack and described Sunday's attack on Nirankari Bhawan as "yet another attempt by Pakistan's ISI and the Pakistan establishment to carry out terrorist actions in Punjab to disturb the peace in the state".

"It was in ISI's interest to keep the border disturbed to ensure internal peace in Pakistan," Amarinder told media here.

"Attempts by Pak ISI and Pak establishment to forge linkages between Punjabi and Kashmiri terrorist groups is a matter of serious security concern for Punjab," the Chief Minister said, adding that the Punjab Police was working closely with central agencies to check the spread of such forces.

Amarinder said that his government was committed to ensuring that nobody was allowed to disturb the state's hard-earned peace and harmony.

The Chief Minister pointed out that there had been only two terror attacks in the state in 2018, including the Maqsudan Police Station attack and Sunday's incident near Amritsar.

"Both were successfully solved by the police, who had also cracked all the cases of targeted killings. The sacrilege cases that had taken place in the last 18 months were also solved," he said.

Giving details, the Chief Minister said that preliminary investigations and CCTV footage of the incident had led to the arrest of Bikram, who has identified his accomplice as Avtar Singh Khalsa (32 years) of village Chak Mishri Khan, Lopoke (Ajnala) in Amritsar district.

Punjab Director General of Police (DGP) Suresh Arora said Bikramjit was riding a TVS motorbike (PB-18-M-7032) at the time of his arrest. Bikramjit's black Bajaj Pulsar motorcycle (PB-02-BF-9488), which he used in the attack, has also been recovered.

"Bikramjit Singh has disclosed that Avtar Singh called him up late on November 3 and asked him to be ready for an assignment the next morning. Around 4.30 a.m that day, Avtar reached Bikram's house and both set out on Bikram's Bajaj Pulsar motorcycle to retrieve the hand grenade from an orchard located at a distance of about 1 km on Majitha-Hariyan link road. They retrieved the HE 84 hand grenade, which had been buried in a half feet deep pit under a Shisham tree," Arora pointed out.

"According to Bikramjit's initial questioning, the recee of Nirankari Satsang Bhawan was carried out on the morning of November 13 when no one was present on the premises. During the recee, the two conspirators especially checked out the locations of CCTV cameras en route, the layout plan of the Bhawan and the distance from the main gate on the boundary wall of the Bhawan to the Satsang Bhawan building," Arora said.

Bikramjit has further said that as decided, on November 16 Bikram reached the house of Avtar Singh at Chak Mishri Khan village on his black Bajaj Pulsar motorcycle at about 9 a.m, where they removed the number plate of the motorcycle. They started for village Adliwal at about 9.30 a.m and covered their faces on the way, near village Manawala. They waited in the area for the crowd to congregate at the Satsang Bhawan. Both of them were armed with pistols at that time, he added.

Bikram told the police that Avtar entered the Satsang Bhawan complex through the open gate, along with the other followers while he himself managed to subdue and take control, at gunpoint, of the two "sewadars" (volunteers) who had been deployed at the two gate-posts of the Bhawan complex.

"After hurling the grenade, both fled on Bikramjit's mobike and reached Avtar's village around 12 noon, where Avtar took back the pistol from Bikramjit. After changing his clothes and appearance, Bikramjit drove back to his village on his black Bajaj Pulsar motorcycle," the DGP said.

According to Bikramjit, Avtar was in touch with one Happy in Pakistan, who had got the hand grenade dumped near the orchard near Majitha through some of his other associates.

Bikramjit has revealed that the geo-location details as well as pictures of the dump location were sent to Avtar on his mobile to facilitate the retrieval of the hand grenade.

"Harmeet Singh Happy had earlier come to notice for supply of a hand grenade (Arges Type HG-84) of the same specifications to Shabnamdeep Singh, r/o Samana (Patiala), a self-styled chief of Khalistan Gaddar Force (KGF), who was arrested by Punjab Police (Patiala) on October 31, 2018," the DGP said.

The Punjab Police had earlier recovered five such hand grenades, as part of a huge consignment comprising AK-47 rifle, MP-9 rifle and seven pistols, which had been sent by terror outfit Babbar Khalsa International (BKI) and ISYF (International Sikh Youth Federation) (Rode faction) across the Indo-Pak border and recovered from the terrorist module of Sher Singh and Mann Singh on May 21, 2017.

"It has been learnt that HG 84 hand grenade is produced by Arges of Austria, and also manufactured in Pakistan Ordnance Factories (POF) of Pakistan (as "84-P2A1"). Such grenades are commonly used by the armies of Pakistan, Afghanistan and Austria. HG 84 is a destructive type of grenade, which causes fragmentation after the explosion and has an effective range of 30-meter radius. These are mainly used to attack and kill a gathering of persons. Such grenades have been used in Jammu and Kashmir in the past," a Punjab Police spokesman said.

Amarinder said that since March 2017, the Punjab Police has busted 17 terror modules and arrested 81 militants, thereby preventing a large number of terrorist actions in the state.

"The Punjab Police has seized 77 weapons from these terrorists, including very sophisticated automatic weapons, RDX and other explosives, as well as 12 hand grenades," he added.

"Since March 2017, at least 3 arms consignments, pushed into Punjab by Pak ISI in collaboration with chiefs of different Pak-based Sikh militant outfits, such as ISYF, Khalistan Zindabad Force (KZF) and KLF, have been recovered by the Punjab Police. These consignments consisted of AK-47 Rifles (5), MP 9 Rifle (1), Pistols (10) and hand grenades (11)," he added.

Bikramjit and Avtar have been booked for murder, attempt to murder and under other sections of the Indian Penal Code (IPC), Arms Act, Explosive Substances Act and Unlawful Activities (Prevention) Act.