Members of the Karnataka Rakshana Vedike went on the rampage at the railway station here on Thursday, while protesting against the release of water from the Cauvery to Tamil Nadu.
The police said that the protesters damaged nearly 20 windows, desks and tables.
They walked into the station in small groups and vandalises the place, the police added.
Jagadish Biradar, KRV district president, and several others suffered injuries. The police have arrested six on charges of damaging public property.