A bomb was exploded outside a polling booth at Madhubani district of the state but no casualties have been reported yet.
Following the case of electoral malpractices, Bihar police arrested at least 150 people from several parts of the state.
According the police sources, a presiding officer was beaten up by local people for playing partisan role at Supaul district.
In another incident at Katihar district, a presiding officer died at a booth of Pranpur just before polling due to cardiac attack.
However, stating about the security situation in various polls, Director General of Police, Neelmani informed, "85 percent of booths were guarded by central paramilitary forces and armed police from other states, the remaining were being looked by the Bihar Military Police."
In the first five hours of polling till 1 pm, 36 percent turnout was recorded, state election officials said.