The Bihar government sealed the state's 114-kilometre border with Nepal on Monday, a day before the second phase of polls in the state.
The State Chief Secretary K A H Subramanian told rediff.com that the border was sealed to prevent entry of troublemakers from Nepal.
The state police fear that a large number of Maoist rebels from Nepal may have already entered the border districts for shelter.
A state administration official said 325 companies of paramilitary forces were deployed across the 82 assembly constituencies, spread over 15 districts, going to polls on Tuesday.
The forces included 115 companies of the Border Security Force and 75 of the Central Reserve Police Force. Besides, 85 companies of the Special Task Force of the Bihar police were also pressed into service.
The government has also issued shoot at sight orders against booth-grabbers in case the security personnel failed to disperse or capture them.
In view of the poll boycott call from the Naxalites, the government has decided to press into service two helicopters for aerial surveillance, the sources said.
The Special Task Force personnel in these choppers will keep in touch with all the police stations through high- frequency wireless sets.
Wherever necessary, these choppers will be used to transport security men.
Nearly 1.8 crore people are likely to vote in Tuesday's election, where 1,015 candidates are in the fray.
With PTI inputs.