Chaotic scenes in the Greek town of Volos.
Protesters attacked police with petrol bombs and rocks, and the authorities responded with tear gas.
The clashes broke out after hundreds of soccer fans protested the demotion of two clubs from the Greek Super League.
Olympiakos Volos and Kavala were sent to division four.
This decision was overturned on appeal but the Professional Sports Committee said neither club had broken ties with their owners who have been accused of match-fixing.
More than 80 people have been charged while Kavala's owner and president have been banned from the sport for life.
Police say 15 people were arrested and several buildings including government offices were damaged.
Lily Grimes, Reuters