Polling was being held in Ranchi, Giridih, Jamshedpur, Singhbhum (ST), Khunti (ST) and Hazaribagh seats under strict security and helicopter surveillance.
Five persons, including four CRPF personnel, were injured in attacks by Maoists, who also blew up railway lines in separate places in the state.
A CRPF patrol was attacked by Maoists who exploded two land mines at Lalpania near Maoist-affected Jhumra Hills in Bokaro district, CRPF (26th Battalion) Commandant, Sanjay Kumar said.
Three CRPF men, Pratap Singh, Surendra Kumar and P C Mandal besides driver Ranjit Kumar were injured. Maoists fired on another CRPF patrol at Tulbul village injuring one of the men and a brief encounter took place before the ultras retreated.
Maoists also blew up a stretch of railway lines between Dania railway station in Bokaro under the South Eastern Railway disrupting train services, Bokaro Superintendent of Police, Jitendra Kumar Singh said.
A pressure cooker bomb was recovered near a polling booth in naxal-hit Saranda forest range of the state, an hour before polling began in the Singhbhum (ST) constituency, Superintendent of Police, N K Singh said.
A report from Giridih said that the Maoists exploded ten bombs at separate places in the Giridih Lok Sabha constituency where polling was on.
The rebels also exploded a bomb at Ghamaria Bharati Chalkari and two at Harladih around 1.30 am.
The first phase of the polls was held in four constituencies on April 10. The third and last phase would be held on April 24 in four seats.