Around 10.04 crore voters will be eligible to exercise their franchise to decide the fate of 568 candidates, including 58 women.
Voting is being held in Alauli (SC), Suryagarha, Tarapur, Jamalpur, Katoria (SC), Belhar, Sinkandra (SC), Jamui, Jhajha and Chakair declared 'Maoist-hit' between 7 am and 3 pm.
Prominent contestants include BJP stalwarts and ministers Ashwini Kumar Choubey (Bhagalpur), Nand Kishore Yadav (Patna Sahib) Ramnarayan Mandal (Banka), besides JD(U) minister Damodar Raut.
Senior IAS officer Afzal Amanullah's wife Parveen Amanullah is contesting on a JD(U) ticket from Sahebpur Kamal.
LJP president Ramvilas Paswan's brother and state party president Pashupati Kumar Paras is contesting from Alauli.
Deputy Speaker of state Assembly and RJD nominee Shakuni Choudhary is contesting from Tarapur.
While JD(U) is contesting from 25 seats, ally BJP is contesting in the remaining 17.
RJD has fielded candidates in 26 and ally LJP in 16. The Congress is contesting from all 42 constituencies while the BSP is in the fray from 40 seats.
The CPI-ML (L) is contesting 15 seats, CPI (13) and CPI-M (six).
"We have made multi-tier security arrangements for holding free, peaceful and fair polls," Director General of Police Neelmani said.
Borders with Jharkhand and Uttar Pradesh have been sealed and close ground and air surveillance being kept, Neelmani said.
Special Task Force (STF) commandos and senior police officials would maintain air surveillance while patrols would be intensified, he said.
The 42 constituencies are spread over eight districts. Byelection in the Banka Lok Sabha seat is also being held simultaneously with the fourth phase of assembly elections.
The two contenders for the seat are Putul Singh (Ind), widow of former union minister Digvijay Singh and former union minister Jayprakash Narain Yadav of RJD.
Both the NDA and the Congress were supporting the candidature of the independent.
The bypoll was necessitated by the death of Digvijay Singh three months ago.
Read more: Polling begins in 4th phase of assembly elections in Bihar - The Times of India http://timesofindia.indiatimes.com/india/Polling-begins-in-4th-phase-of-assembly-elections-in-Bihar/articleshow/6850355.cms#ixzz1402LkRoP