The incident occurred at Laxmaniatari village last night as a festering dispute over land turned violent. The two siblings attacked members of their family with an axe hacking three of them, including parents, to death, while injuring as many others, Belhar police station in-charge Anil Paswan said.
The victims were identified as Sindho Tanti (60), his wife Chameli Devi (52) and brother in-law Arvind Tanti (40), he said, adding the bodies were recovered from a nearby field and sent for post-mortem.
The duo managed to escaped from the spot, Paswan said, adding raids were being carried out to nab them.