A powerful bomb explosion triggered by suspected Maoists has killed at least six policemen and wounded several others in eastern India.
The casualties came after a hidden mine targeted police vehicles over a small bridge in Bihar's , the dpa reported.
The incident comes as a month-long electoral process to choose the state legislative assembly is taking place in the volatile region.
Security has been tightened and hundreds of additional troops have been deployed in several districts across the state.
The militancy has now spread to 20 of the 28 Indian states. Bihar is one of the several states in the east and central India where Maoists groups are active.
The rebels, who are supported by tribal groups and landless farmers, have fought against state and central government for many years. Over 6,000 people have died in Maoist-related clashes over the past three decades.
says the Maoists are the gravest threat to the country's internal security.