At least 10 people were arrested and 40 detained Friday in the Greek capital after an annual memorial march for a 15-year-old boy who was killed by police in 2008, local media reported.
Tension rose as protesters threw Molotov cocktails at police who surrounded the Exarcheia area where the teen was shot dead 11 years ago.
Thousands of officers were deployed earlier in the day as the city closed the main central metro stations and streets.
Four bus stops where damaged when groups of hooded protesters threw petrol bombs, marble, stones and other objects at police.
Riot police responded with tear gas.
More than 5,000 protesters took part in an evening march, including anarchists and anti-establishment organizations, according to police.
A peaceful march led by thousands of students took place earlier in the day.
At least 22 stores and public buildings were damaged in Athens overnight, according to reports.
Police said seven people have been detained after the attacks, but were released due to lack of evidence.
Alexis Grigoropoulos was shot dead by police officer Epaminondas Korkoneas on Dec. 6, 2008 after officers approached a group of teens and allegedly provoked them. A verbal exchange ensued which led to the boy’s murder.
Grigoropoulos’ death triggered the worst riots seen in Athens since the fall of the Greek dictatorship in 1974.