Police clashed with demonstrators in Athens as thousands attended rallies to mark the fifth anniversary of the fatal police shooting of a teenager that triggered major riots for three weeks.
Police said four officers were injured in yesterday's clashes 17 people were arrested for causing public disturbances and 184 detained for questioning.
Several hundred youths hurled rocks and petrol bombs at police, burned two cars and set fire to piles of rubbish after about 5,000 protesters held two separate marches. Police used tear gas, pepper spray and stun grenades against the rioters.
Alexis Grigoropoulos, 15, was killed on the night of December 6 2008 when a policeman opened fire following an argument in the centre of Athens.
Within hours of the boy's death, thousands of youths took to the streets across the country. The riots that ensued were Greece's worst in decades and buildings and shops on major streets were burned and looted in the capital.
The riots occurred a year before Greece was plunged into a financial crisis and protesters at anniversary events have often opposed the government and the "troika" of bail-out inspectors from the European Union, the European Central Bank and the International Monetary Fund.
Police remained on alert in several cities, including Athens, where more protests were expected.
In Thessaloniki, Greece's second largest city, demonstrations coincided with the funeral service for a 13-year-old Serbian girl known only by her first name, Sara, who was found dead last weekend.
The tragedy happened after her unemployed mother used a barbecue to try to heat their home which had its electricity supply disconnected. A coroner said the girl died of carbon monoxide poisoning.
Protesters gathered outside the church where the service was held, and chanted: "They killed little Sara. This is what the troika means."