Police arrested Maharashtra Navnirman Sena (MNS) chief Raj Thackeray on Wednesday for inciting violence after his party's workers attacked north Indians who migrated to the city.
Extra police officers and paramilitary forces were posted around the city before Thackeray was arrested. He was later released on bail.
Police also arrested Abu Azmi, a local leader of the Samajwadi Party, which is based in Uttar Pradesh. He is accused of encouraging north Indians in Mumbai to retaliate and has also been released on bail.
Shops closed in parts of the city, either as a precaution against trouble or because they were forced to by party workers.
Media reports said a 55-year-old was killed after workers threw stones and damaged buses in Nasik.
There were also reports of protesters throwing stones and attacking vehicles in other parts of Maharashtra, as well as on the outskirts of Mumbai.
Police had been under pressure to arrest Thackeray since Sunday, when party workers attacked cinemas screening films in Bhojpuri and beat up dozens of north Indians, including some of the many north Indian taxi drivers.
Television pictures showed Thackeray wearing a blue sleeveless jumper over a white shirt, walking calmly towards a Mumbai court, surrounded by policemen.
For generations, poor Indians have left behind rural poverty to try and make a living in Mumbai and other big cities. Millions hail from Uttar Pradesh and Bihar, two of India's poorest states.