Chandigarh: The Punjab Police has found striking similarities between the modus operandi of the perpetrators of the grenade attack at a Nirankari congregation in Amritsar and the one allegedly planned by an ISI-backed terror module busted in Patiala early this month.

The Punjab Police had nabbed on November 1 Shabnamdeep Singh alias Maninder Lahoria, who "confessed" to the police that he was asked by his Pakistani handlers to target police posts and crowded places during festivals.

Besides a motorcycle, Lahoria was found in possession of a pistol and a hand grenade - the weapons used by the two perpetrators of the Sunday grenade attack, in which two motorcycle-borne assailants had barged into the Amritsar Nirankari Bhawn, brandishing a pistol and lobbed a grenade at devotees, pointed out police officials.

Lahoria was also found having letter pads of "Khalistan Gadar Force" and other terror outfits, said police officials, probing the Amritsar grenade attack.

Punjab Chief Minister Amarinder Singh had Monday described the grenade attack as a suspected handiwork of the ISI-backed terror modules.

Prima facie, this appears to be an act of terror by separatist forces, organised with the involvement of ISI-backed Khalistani or Kashmiri terrorist groups, Singh had said.

There are a lot of similarities between Amritsar grenade attack and what Lahoria had planned to do in the state, a senior official of Punjab police said Tuesday, adding Lahoria too had planned to spread terror by lobbing a hand grenade at a crowded place.

Lahoria, who was arrested from Patiala, has confessed that he was getting instructions from his handlers in Pakistan and was promised Rs 10 lakh for each act of violence, the police official said.

The Punjab police also suspects the involvement of Pakistan-based Khalistan Liberation Force (KLF) leader Harmeet Singh alias 'PhD' in the Amritsar grenade attack.

Harmeet Singh had been accused of radicalising youths in Punjab through social media, an official said.

Pakistan-based handlers seek to radicalise youths here through internet to incite them to spread terror in Punjab, the officials added.

Initial investigations into the Amritsar case suggested the grenade used in the attack was similar to the ones manufactured by Pakistani army ordinance factories, the Punjab CM had said Monday, adding that the government has taken serious note of the incident and was "aggressively pursuing all angles of investigation".

Asked if the police had been able to get any clue about the duo behind the Amritsar grenade attack, a police official said, We are on the job.

The state government has already announced a reward of Rs 50 lakh for anyone providing information, leading to the duo's arrest.

Radical outfit Dal Khalsa's spokesperson Kanwarpal Singh, meanwhile, claimed in Amritsar Tuesday that two persons - Paramjit Singh Mand and Gurjant Singh - have been asked to appear before police.

While accusing the police of not following the legal procedure in summoning people, Kanwarpal Singh said the police came to their houses in wee hours of Tuesday and told them to appear before it.

The Dal Khalsa spokesperson claimed Mand has been asked to appear before Batala SSP while Gurjant was taken in custody.

He also claimed several more youths have been summoned by the police for questioning in connection with the grenade attack.

The Bathinda police, meanwhile, inspected over 190 paying guest accommodations at Ajit Road to keep a check on anti-social elements.

Nothing incriminating has been found, said Bathinda SSP Nanak Singh.

He said two persons who were earlier detained during the checking were released after nothing suspicious was found on them.

In Ludhiana, the Government Railway Police pasted posters ofZakir Musa, the chief of Jammu and Kashmir-based terror outfit Ansar Ghazwat-ul-Hind with reported links to Jaish-e-Mohammed (JeM). Earlier his posters were put up in Gurdaspur district.

Last month, Punjab police had arrested three Kashmiri students ofJalandhar's CT Institute of Engineering, Management and Technology, allegedly linked to Ansar Ghazwat-ul-Hind.

The police had also recovered weapons, including an assault rifle, from them.

In the wake of Amritsar grenade attack, the Punjab Police has beefed up security arrangements in the state and stepped up highway-patrolling and checking of key installations and busy places.