Rashtriya Janata Dal (RJD) leader Ravinder Yadav was killed by unidentified assailants on Friday, a day after he was reported to have a heated exchange of words with some of his political rivals.
Media reports quoted family members, as saying that Yadav was shot dead outside his home in Bihar's Supaul District.
The incident resulted in a violent protest by his supporters, some of whom blocked roads and burnt tyres, police said.
Additional security forces have been deployed in the area to prevent further untoward incidents.