In Chhattisgarh, at least 4 policemen were killed and three injured in a landmine blast in the Dantewada district last night. The deceased include a sub-inspector. One policeman is reported missing after the blast. The injured have been admitted to the local hospital. According to the police sources, naxalites triggered a landmine at a vehicle-borne police party near Perpa under Kirandool police station area of the district late last evening and resorted to indiscriminate firing soon after the blast .Police have launched a search operation after the incident.