Trouble erupted when some Muslims objected to music being played by the Kanwariyas or the Shiv devotees who were returning from Haridwar.
Outraged, the Kanwariyas resorted to violence, vandalized shops and public property and set on fire many vehicles in the Jogi Navada locality, a police officer said.
One person was killed in the firing in Math Chowki area.
According to police, at least two dozen people were injured in the violence that broke out in many parts of the city and continued past midnight.
Hundreds of people emerged from their houses in Shahdana area while a police team was attacked in Azamnagar.
Many policemen, including the superintendent of police (SP), were injured in the stone pelting.
Police lobbed tear gas shells at the mobs but could not contain the violence.
Senior police officials, including the Additional Director General of Police Jag Mohan Yadav, rushed to Bareilly early Monday morning to contain violence and restore normalcy.
The Bareilly district administration has clamped curfew in the city.
Soldiers of the provincial armed constabulary have been deployed at several sensitive localities, an official told IANS.