The incident happened late on Thursday in the Poisar slum colony in the north-west suburb of Kandivali, said an official of Samata Nagar Police Station.
According to investigations, Durgesh L. Thakur, 21, who worked in a private company in Pune, insisted on stepping out of the house during the lockdown period to buy some essentials.
His elder brother Rajesh L. Thakur, 28, who runs a saloon, and his wife tried to stop him from going out, but the adamant younger brother refused to heed them.
In the huge altercation that followed, Rajesh allegedly picked up an iron pan and rod and brutally assaulted his younger brother, who subsequently died of severe injuries.
He has been arrested on charges of murder and further investigations are on, said an official. He was produced before a court on Thursday and sent to police custody.(IANS)