Deputy Superintendent of Police, Khargpur, Ranjan Kumar told PTI that the security personnel belonging to 131 CRPF battalion were travelling in two jeeps to Tarapur in the Maoist-affected district for poll duty in the early hours when the attack took place.
The Maoists first detonated an improvised explosive device and then ambushed the CRPF personnel near Sawa Lakh Baba Mandir at the entrance of Bhimbandh jungle at around 5.30 AM. The security personnel returned the ultras' fire.
The dead CRPF personnel have been identified as head constable Ravindra Rai and constable Sone Gora, Kumar said, adding their bodies have been kept at Kharagpur police station.
The seven injured have been rushed to Bhagalpur hospital, he said.
Maoists had earlier given a call for a poll boycott.
Lok Janashakti Party President Ram Vilas Paswan's son Chirag is in the fray from the Jamui parliamentary constituency against Bihar Assembly Speaker Uday Narayan Choudhary of JD (U) and Sudhanshu Shekhar Bhaskar of RJD.
In another incident, Gaya Police seized six can bombs weighing 30 kg each from Banke Bazar area under Imamganj Assembly segment, which is part of Aurangabad Lok Sabha seat, where too polls are underway.
The bombs were defused, Gaya senior superintendent of police Nishant Tiwari said.
Brisk voting is on in the six constituencies where polling is on in the state.
Election office sources said above seven per cent votes were cast in the first two hours of polling in Sasaram(SC), Aurangabad, Karakat, Gaya (SC), Jamui (SC) and Nawada.