The sisters Dolly (25) and Jolly (22) were hacked to death and their mother and aunt injured after they were attacked by the gang at their house last night, Senior Superintendent of Police (SSP) Nishant Tiwari said.
The bodies have been sent for post-mortem and the injured women admitted to Anugrah Narayan Magadh Medical College, he said.
A mobile phone has been recovered from near the girls' bodies, Tiwari said.
The motive behind the attack was not clear.