Vidarbha Rajya Andolan Samiti members, who were holding a rally here on Tuesday demanding a separate state, alleged that police assaulted them during the protest.
The organisation was demanding separate Vidarbha state on the occasion of Maharashtra Foundation Day when the police also detained their members.
"Police have every right to arrest us but they cannot beat us. Just now, I saw a policeman thrashing a man on his face. There was no reason for it, that man had already been caught," an angry protester told reporters.
Vidarbha is the eastern region of Maharashtra, which was merged into the new state of Maharashtra in 1960. Since then, there has been a demand of a separate state of Vidarbha with Nagpur as its capital, as some individuals and organisations argued the region was less developed and financially weaker in comparison to the western part of the state.
While Chief Minister Devendra Fadnavis has maintained that the decision lies in the hands of the central government, BJP's estranged ally Shiv Sena has strongly opposed the demand.
Maharashtra Foundation Day or Maharashtra Diwas is celebrated every year on May 1, as on this day erstwhile Bombay State was divided into Maharashtra and Gujarat in 1960.