Till 11 am, 22.42% voter turnout in Araria, 20.3% in Bhabua and 19.2% in Jahanabad was recorded.
The bypolls are being seen as a litmus test for Chief Minister Nitish Kumar after he pulled out of the state's grand alliance and joined the BJP.
The Araria seat fell vacant after the death of Rashtriya Janata Dal (RJD) MP Mohammad Taslimuddin. The key contenders for the seat are RJD's Sarafaraz Alam, Taslimuddin's son, and the BJP's Pradip Singh.
The Bhabua assembly seat got vacant after the death of BJP's Anand Bhushan Pandey, and the party has fielded his widow Rinki Rani Pandey. Another key candidate for the seat is Shambhu Patel from Congress.
The death of RJD MLA Mundrika Singh Yadav necessitated the bypoll for Jehanabad seat, and his son Uday Yadav is contesting for the seat. Another key candidate in the fray is JDU's Abhiram Sharma.
On the same day, the Lok Sabha by-election for two constituencies of Uttar Pradesh, namely Gorakhpur and Phulpur were also held.
The results for both states will be declared on March 1.(ANI)