Ravinder Yadav was killed by unidentified men after he was asked to step out of his house early Friday.
Angry over the killing, hundreds of Yadav's supporters blocked roads and burnt tyres.
Tension prevailed in the area but the situation was brought under control as additional security forces have been deployed, police officials said.
His family members and supporters termed his killing a political killing planned by his rivals.
Yadav had a heated argument Thursday during Lok Sabha polls in Supaul parliamentary seat and he received life threats, his family members told police.
He had contested 2010 state assembly polls as a RJD candidate against JD-U's Bijendra Prasad Yadav.