Around 150 masked youths attacked banks, state buildings and a police training facility car park in the Athens district where a teenager was shot dead by a policeman two weeks ago sparking nationwide unrest.
According to Greek state television NET, there were no reported injuries.
The violence began shortly after a memorial commemoration at the site where 16-year-old Alexandros Girgoropoulos was killed by a policeman two weeks ago.
More than 100 people have been injured and about 400 have been detained during two weeks of protests in Greece triggered by the police shooting death of the teenager. Hundreds of shops and banks have been firebombed, vandalized and looted.
The policemen accused of killing the youth have been detained and charged with manslaughter.
Clashes in Hamburg
Meanwhile a rally held in Hamburg to show solidarity with the Greek protestors turned violent as police clashed with some 800 demonstrators in the German port city.
Police broke up the protest after bottles and fireworks were thrown at officers as the demonstrators attempted to march from the University of Hamburg to the city's main railway station.
Afterwards, some of the protesters gathered outside the Greek consulate-general for an evening vigil. Police, backed by water cannons, were out in force near the building.
Police said some of the Hamburg demonstrators wore face masks and threw bottles and burning missiles at the police, two of whom needed hospital treatment.