Polling began under heavy security on Wednesday morning in 15 of Bihar's 243 assembly constituencies. The polling in these four Naxalite-hit districts was scheduled for November 13 but deferred due to security reasons.

Indian Air Force helicopters were maintaining aerial surveillance and borders with Nepal have been sealed. Nearly 32,000 security personnel, including about 15,900 Central forces, have been deployed at 3,415 booths for patrolling in North Bihar's East Champaran, West Champaran, Sitamarhi and Madhubani districts, state Home Secretary H C Sirohi told PTI.

• Bihar sees 45 percent voting in 3rd phase

Over 31.74 lakh voters will decide the fate of 119 candidates, including two ministers in the erstwhile Rabri Devi government - Rama Devi of Rashtriya Janata Dal (Motihari) and Vishwamo Ban Sharma of Congress (Chanpatia).

"Since polling is being held in these constituencies against the backdrop of Sunday night's Naxalite onslaught in Jehanabad, we are leaving nothing to chance," Sirohi said, adding that Central Para-Military Forces were patrolling by air and on water.

While NDA allies,  Janata Dal (United) and Bharatiya Janata Party, have fielded candidates in eight and seven seats respectively, Secular Democratic Front partners RJD, Congress and Communist Party of India - Marxist have put up nominees in 10, five and two seats respectively.

CPI-M nominees are engaged in friendly contests with RJD at Sugauli and Congress at BISFI. Lok Janshakti Party and Communist Party of India are contesting 13 and two seats respectively.

Complete coverage: The Bihar polls