At least four militants were killed during a security operation in the southern Pakistani city of Karachi, said a police official Wednesday. Senior Police officer Chaudhry Aslam said that the operation resulted in four militants being wounded in an exchange of fire with the police. Two policemen also sustained injuries during the encounter which saw the militants succumbed to their wounds while treated in hospital. Police said that huge cache of firearms and explosives were also recovered during the operation. Earlier, the Federal Cabinet approved an operation led by the paramilitary forces against militants in Karachi