Rivals of one Kamlesh Rai of Purhara village stormed Rai's house and stabbed him and five others, they said.
Kamlesh Rai (55), Satyendra Rai (50), Shanti Devi (45) and Vikas Kumar (22) died in the attack, police said.
The other two, who were injured in the incident, were admitted to a hospital.