Greek police fired tear gas on Saturday after protesters hurled petrol bombs in Athens at an anti-racism rally.
Clashes erupted after hooded demonstrators broke off from a peaceful march.
It marked four years since the killing of an anti-fascism rapper by a supporter of Greece’s far-right, ultra-nationalist party, Golden Dawn.
“We must close down the headquarters of this Nazi organization,” said protester Alexandra Martini.
“It is not a political party. Its offices are used to prepare racist attacks. From Greece to America, we are here to say that we will smash the fascists”.
With a trial of Golden Dawn members still ongoing, the crowd demanded swifter justice for rapper Pavlos Fyssas and other victims.
Another protester, Maria Kaskarika, says a Golden Dawn member was arrested over an attack on her 24-year-old son last March.
“Everyone should stand against the Nazis…because Nazis attack everyone,” she said.
“We must stand united and set an example for anti-fascist movements around the world.”
Another rally marking the rapper’s death has been called for Monday in the working-class neighbourhood of Keratsini where he was fatally stabbed.
Our correspondent in Athens, Michalis Arampatzoglou, says: “Far-right violence did not stop at Pavlos Fyssas. In the first half of 2017, Greek police recorded at least 27 attacks with a possible racist motive against refugees or immigrants. The number is estimated to be higher, as many victims are afraid to report the attacks”.