Hundreds of protesters surrounded a regional governor's residence in northwest Azerbaijan on Thursday to demand his resignation after a night of rioting in which cars and buildings were set ablaze.
Police said several protesters and several police officers had been injured in the town of Ismaili, about 200 km (125 miles) northwest of the capital Baku, after the rioting began following an incident involving a car.
The police said they had been forced to bring in reinforcements to help restore order after the protesters threw stones at them.
It was not immediately clear whether the protesters had demands other than the governor's resignation, or how bad the damage was from the rioting.
Sandwiched in the Caucasus region between Russia, Iran and Turkey, Azerbaijan supplies Caspian oil and gas to Europe.
Western governments and human right groups accuse President Ilham Aliyev, who succeeded his father in the former Soviet republic in 2003, of authoritarian rule and say he has clamped down on dissent.