An estimated 20 per cent voters exercised their franchise on Monday as polling passed off peacefully for by-election to the Patna (West) assembly constituency held amid tight security.

District election control room sources said 19.85 per cent of over 5.12 lakh voters participated in the exercise, which was a peaceful affair.      

Polling remained dull throughout the day as little enthusiasm was seen among the voters.

No electoral malpractice was reported from anywhere in the constituency where two companies of Central Reserve Police Force, four of Bihar Military Police, 350 personnel of the newly-raised State Auxiliary Police consisting of ex-armymen, besides district armed police jawans were deployed at all the 531 polling stations, official sources said.

Monday's poll will decide the fate of 13 candidates, including Bharatiya Janata Party's Nitin Navin, Congress' Rana Ajay Singh and Samajwadi Party's Chandan Rai. Rashtriya Janata Dal and its allies Communist Party of India-Marxist and Nationalist Congress Party extended support to the Congress nominee.

The by-election was necessitated following the death of BJP legislator Navin Kishore Prasad Sinha, whose son Nitin Navin has been fielded by the saffron party.

Bihar Pradesh Congress Committee chief spokesman Prem Chandra Mishra alleged that state BJP ministers, Ashwini Choubey and Prem Kumar, were seen moving freely in the constituency during the poll and urged the Election Commission to order registration of a first information report against them for violating the model code.

Mishra also demanded arrest of state BJP spokesperson and legislative council member Kiran Ghai for allegedly influencing the poll at a booth in the constituency.