Thousands of youths have marched in Athens two years to the day after police killed a teenager, triggering the worst riots Greece had seen for decades.
Police fired tear gas and percussion charges as some of the protestors threw missiles at riot officers to mark the anniversary.
There were clashes with around 500 militants near the parliament.
Police say the demonstrators, most of whom covered their faces with hoods, threw three petrol bombs.
They also hurled red paint at the Bank of Greece building.
Roads in central Athens had been closed, and many shops had boarded up their windows in anticipation of trouble.
Fifteen year old Alexis Grigoropoulos was killed in 2008.
His death triggered widespread violence that paralysed the Greek capital for weeks.
At the spot where he died, many gathered and stood in silent remembrance.
Two policemen were convicted of his murder earlier this year.
Athens demos on anniversary of youth killing