The incident occurred yesterday when Palenti Devi, her husband Sukhbir Singh and son Bijender were sleeping in their house in Jagahheri village here, SHO Munender Singh said.
He said the assailants hit the victims with sticks, killing the woman and injuring her husband and son.
The body of the deceased has been sent for postmortem while the injured have been admitted to a hospital, the SHO said.
Police said they are trying to ascertain the cause of the incident.
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Police said investigation is underway to identify the deceased while his body has been sent to a mortuary.
In another incident, 40-year-old Ishrat Jahan was beaten to death by her in laws over a property dispute in Sikri village here.
According to SHO P P Singh, Jahan's husband had died four years ago, following which there was a property dispute between her and her brother-in-laws.
He said investigation into the case is underway and her body has been sent for postmortem.