Anarchists set fire to a public transport bus and several cars in central Athens during clashes with police on Tuesday evening.
The violence followed a large demonstration that was in support of a jailed anarchist who is on hunger strike in an effort to leave prison to attend university.
Riot police retaliated with tear gas to dispel stone-throwing rioters. Despite the fiery scene, no arrests or injuries have been reported following the riot.
However, at least 15 people were arrested earlier in the day when between 8,000 and 10,000 people marched through central Athens in solidarity with Nikos Romanos, a young anarchist convicted of involvement in an armed bank robbery.
He has refused food for the past three weeks after authorities said they wouldn't let him attend lectures at an Athens university, where he was admitted after taking entry exams in prison.