Boutaris was attacked by a group of nationalist extremists at a ceremony of commemoration of Pontic Genocide victims on Saturday. The official was reportedly approached by a dozen of people telling him to leave the event, and then kicking and attacking him with bottles. Boutaris was taken to a hospital for treatment and kept there overnight.
Boutaris is known for his statements favoring the strengthening of trade ties with Turkey and support for Thessaloniki gay pride parade.
Greek government officials and opposition condemned the attack on mayor as "fascist."
In 2012 Boutaris was chosen as 'the best mayor of the world' for the month of October by the Britain-based City Mayors Foundation.