Fierce clashes between police and protesters took place in Athens on Saturday on the anniversary of the killing of a teenager by police six years ago.
Shops were set on fire and many others damaged. Over hundred people were arrested.
The anniversary of the killing of Alexandros Grigoropoulos, who was 15 at the time, normally brings thousands of anti-state demonstrators on to the streets.
But this year tensions have been raised over a self-proclaimed anarchist who witnessed the killing in 2008, and is now on hunger strike over the Greek authorities’ refusal to let him attend university classes.
Nikos Romanos is currently serving a sentence for robbery but is now in hospital in a critical condition.
Saturday’s riots and demonstrations centred around the Athens neighbourhood of Exarchia, inhabited by many people associated with the anarchist movement.
The government appealed for calm in the days leading up to the protest and offered to amend a law to allow prisoners to follow university courses via distance learning.
Romanos however is reported to be insisting on attending classes in person.
“I won’t back down”, he said. “Struggle until victory or struggle until death”.
Euronews correspondent Fay Doulgkeri said the only hope of lowering the tension on the streets could lie in a meeting between his parents and the prime minister on Monday.