Amritsar Nirankari Bhawan attack could be the handiwork of Khalistani separatist who could have been backed by ISI and Mumbai blast mastermind Hafiz saeed. The sources said Al Qaeda terrorist Zakir Musa also reportedly met some suspicious people in Amritsar who could be a part of Khalistani terror group sleeper cells. It is suggested hand grenade used by attacker was supplied by ISI.