There were incidents in central Athens on Monday evening when riot police deployed tear during a protest against the fatal police shooting of a 20-year-old Roma man at the weekend.
Nikos Sabanis was shot dead by police after a car chase in Piraeus on Saturday morning.
Tensions flared on Panepistimiou Ave as police tried to disperse protestors.
Witnesses say there were hand-to-hand clashes, with riot police using tear gas and flash grenades.
The demonstration was attended by groups from the extra-parliamentary left, anti-authoritarians and the MeRa25 party, which is represented in parliament.
Many of the banners held by protestors referred to “police violence.”
Seven officers involved in the shooting dead of Sabanis were arrested on Sunday for intentional homicide.