At least four people were killed and four others injured when some unidentified militants exchanged fire with each other and hurled hand grenades at a police party that arrived at the crime scene to disperse the miscreants in Pakistan\'s southern port city of Karachi on Friday night, local police said. Imran Shaukat, Senior Superintendent Police, said that that two groups of people armed with automatic weapons opened indiscriminate fire at each other and hurled grenades at policemen in Bilal Colony area of Karachi, killing one man at the spot and injuring seven others including one policeman. The injured people were shifted to the Jinnah Hospital of the city where three of the injured succumbed to their injuries. Earlier reports said that at least three people were killed and four others injured in the blast but later police said that it was armed clash between two rival groups. Friday night\'s attack bring the death toll in separate incidents of violence in Karachi to 15 since morning. The dead people included including a member of the provincial assembly of Southern Sindh province who was shot down by unknown gunmen after Friday prayer in North Nazimabad area of the city.