The mayor of Greece's second city Thessaloniki was hospitalised early on Sunday after an assault by suspected far-right members at a rally, officials said.
Yiannis Boutaris, 75, had to be escorted from an event commemorating the massacre of Black Sea Greeks in Turkey during and after World War I when members of the crowd turned violent.
"They were hitting me everywhere. Kicks, punches, the lot," Mr Boutaris told state agency ANA Sunday. "It was a despicable attack, but I am well."
Footage from the event shows Mr Boutaris initially being heckled. As he starts to leave, people start throwing objects at him and he falls to the ground.
Some of the attackers tried to break the windows of his car as it sped off.
The office of Prime Minister Alexis Tsipras said the attackers were "far-right thugs".
A maverick politician, Mr Boutaris has repeatedly angered hardliners in Greece with controversial statements on Macedonia, Turkey and Israel.
Among them is calling Kemal Ataturk, founder of the modern Turkish state and a hate figure in Greece, a "great leader".