Patna, Sep 17 - In a major setback to Bihar Chief Minister Nitish Kumar, the opposition Rashtriya Janata Dal (RJD) and its ally Lok Janshakti Party (LJP) Thursday won eight seats in by-elections for 18 assembly seats in the state.

The ruling Janata Dal-United (JD-U) won two seats (Triveniganj and Bagha) and its ally the Bharatiya Janata Party (BJP) won one seat (Begusarai).

Former railways minister Lalu Prasad's RJD won on Bochaha, Kalyanpur, Phulwarisharief, Aurai and Ramgarh seats while former union minister Ram Vilas Paswan's LJP won Warisnagar, Araria and Bodh Gaya seats.

The Congress won Chenari seat and the Bahujan Samaj Party emerged victorious in the Chenari constituency.

The RJD was leading on one seat for which counting is underway, while JD-U is ahead on two seats.