Unknown men exploded four bombs at separate spots in the city within 10 minutes' time yesterday evening, but no one was reported injured. One Jihad, identifying himself as the general secretary of an international terrorist network of Khulna region, claimed the responsibility of the incident. Witnesses said the bombers from a speedy autorickshaw hurled the first bomb on a playground of the Youth Development Club at 7:40pm where two leaders of Awami League and BNP city units were playing badminton. The second bomb exploded within a couple of minutes in front of the house of sadar upazila Chairman Abul Siddique in Ailchara area. The two other bombs were blasted in front of a pharmacy in Puraton Bazar area, breaking the shop's