Prabhawati, 80, was killed in Sector 4 when she was alone in her house, said a police officer.

Footage of a CCTV camera has shown suspicious movement of a woman near her house around the time the crime took place.

"The widow lived with her son, daughter-in-law and two daughters. All four were out of house," Joint Police Commissioner Vivek Sharma told IANS.

The murder came to light when her daughter-in-law, a school teacher, returned home after 2 in the afternoon.

The victim's hands and legs were found tied with ropes. A cloth was tied on her mouth, police said.

The assailants tried to burgle the house but did not do so out of fear of getting caught, police said.