Three people have been injured in Athens after a rally marking the death of a 15-year-old youth by a police officer's bullet 10 years ago turned violent.
A total of 13 people were arrested early on Friday, state television reported, citing police.
In the Exarchia district of Athens, anarchists lobbed hundreds of petrol bombs at police officers and used rubbish containers and other items to erect barricades.
Police used tear gas and water cannon to clear the area, according to reporters at the scene.
The flare-up of violence followed peaceful protests on Thursday by young people marking the death of young demonstrator Alexandros Grigoropoulos in 2008 and protesting high unemployment in Greece.
Unrest was also reported at similar rallies in Thessaloniki, Volos und Patras.
The anniversary of Grigoropoulos' death has repeatedly sparked protests over the years.
The Greek capital saw an unprecedented outbreak of violence and considerable material damage after the young man's death in 2008.
The officer who fired the shot that killed Grigoropoulos was sentenced life in prison in October 2010.
Australian Associated Press