The iron rod has been seized by a police team, police said. (Representational)

A man was arrested for allegedly killing his 60-year-old mother-in-law after hitting her with an iron rod following a heated argument in Delhi's Rohini area on Tuesday, police said.

The incident took place when the elderly woman, Ramkali, a domestic help, was going to work. Her 44-year-old son-in-law Rajesh confronted her about his wife that led to the argument, Deputy Commissioner of Police (Rohini) S D Mishra said.

Rajesh then allegedly hit his mother-in-law with the iron rod that was lying on the ground which injured her on her head.

Meanwhile, the crowd at the spot caught hold of Rajesh and thrashed him until he became unconscious. One among them informed police about the quarrel, DCP added.

Investigations revealed that Rajesh, who works as a painter, and his wife, Vimla, were married for more than 25 years. He would often reportedly beat her up.

Vimla had come to her mother's house on Monday night after Rajesh allegedly beat her, the officer added.

The woman and her son-in-law were admitted to a nearby hospital where she was declared brought dead, while Rajesh is stated to be stable, the DCP said.

The iron rod has been seized by a police team, police said.