A senior leader of major insurgent outfit, United National Liberation Front (UNLF) has been arrested by security forces from Bishenpur district. Official sourcessaid in Imphal today, a massive manhunt was launched at Kabowakching area yesterday following reports of movement of insurgents. During the search operation, a self-styled major of UNLF was arrested. Sources said his interrogation led to the arrest of three sympathisers of the outfit . In another incident, a powerful bomb attached to a two wheeler was seized from the gate of a school at Sangakpham area in Imphal West district which was later defused.The sources said, motive behind the incident was not known but police said they would investigate whether it was connected with monetary demand from the local residents by some militants.