In Bihar, five policemen were killed in a land mine explosion triggered by the Maoists in Sheohar district last night. State Director General of Police Neelmani said an officer in-charge of Shyampur Bhitha police station and four jawans of Special Auxiliary Police were killed in the land mine explosion triggered by the Naxals near Chitikahi bridge. One seriously injured policeman has been admitted to hospital.He said a massive combing operation had been launched to nab the Maoists responsible for the blast. The Maoists have given a call for the boycott of Assembly elections in Bihar.