Sashastra Seema Bal units deployed along the long and porous border have been directed to keep strict vigil on the possible cross-border movement of the ultras.
"There is apprehension that Naxals, after resorting to violence, may sneak into Nepal. So, the extra vigil is absolutely necessary," an official said.
Of the six-phased polls, the last two phases are crucial as they fall in Maoist-dominated areas and the Central government has sent 35,000 paramilitary personnel to assist the state forces to conduct free and fair polls.
The first phase of the poll was held on October 21 and the second phase today. The remaining phases will be held on October 28, November 1, 9 and 20.Six policemen were killed on Friday night as armed Maoists triggered a landmine blast blowing up a jeep on patrol in Bihar's Sheohar district.
India and Nepal share a highly porous 1,751-km-long border which passes through Uttarakhand, Uttar Pradesh, Bihar and West Bengal.