A city official says the mayor of Greece's second-largest city has been hospitalized with head, back and leg injuries after being set upon by nationalist extremists.

Thessaloniki City Council President Calypso Goula said Mayor Yiannis Boutaris was attending a flag-lowering ceremony Saturday in commemoration of the so-called "Pontic Genocide," the killing of ethnic Greeks by the Turks during World War I and the subsequent Greek-Turkish war.

Goula, who also was there, says about a dozen people approached the 75-year-old Boutaris and told him to leave the event, then attacked him with bottles. The mayor is known for his strong anti-nationalist stance.

Goula says Boutaris fell down and was kicked in the head and legs. She says during a church service earlier commemorating the victims, attending politicians were booed.