Three persons including a father-son duo were killed by militants in Manipur's Bishnupur district on Friday night while another three sustained bullet wounds following heavy exchange of fire between state forces and armed men in the same district even as the 24-hour general strike called by the coordinating committee of 27 assembly constituencies paralysed normal life in Imphal valley, police said. The three were gunned down while they were sleeping and their bodies were later slashed with swords at Kwakta in the district by unidentified men, police said on Saturday morning, adding that the assailants came from Churachandpur. "The three used to stay in a relief camp but had returned to their residences at Kwakta on Friday after the situation improved," police said.