The accused, identified as Shatruhan Singh Penkra (26), was neighbour of the deceased. He was arrested soon after the incident on Sunday, they said.
The incident occurred when the woman, identified as Shiv Kunwar, was working in field along with her daughters Suraja (18) and Chanda Kumari (15), said Balco police station incharge Vivek Sharma.
He said Penkra attacked Kunwar without any provocation and hit her on the head before fleeing.
She died on the spot, Sharma said, adding that Kunwar's daughters raised an alarm and tried to catch Penkra.
Police said a case of murder has been registered against Penkra, who they said is deranged.
