Demonstrators commemorating a bloody 1973 student uprising against the military junta then ruling Greece clashed on Tuesday with police trying to enforce a ban on public gatherings imposed to combat the spread of the coronavirus.
Police fired teargas and used water cannons to disperse protesters who tried to march through the capital Athens, disregarding the ban which the government said was vital to protect public health during a pandemic.
Leftist and Communist opposition parties slammed the decision as "authoritarian".
Earlier in the day, police did not intervene as dozens of Communist KKE party members wearing masks and heeding social distancing rules held a separate rally in the centre of Athens to mark the uprising anniversary.
In the morning, Greece's president, political parties and citizens laid a wreath and flowers at the empty Athens Polytechnic University to honour the dozens killed during the student revolt near the end of the junta's 1967-74 rule.
On a day like this in any other year, the campus in central Athens would be teeming with people queuing to pay homage to those killed in the uprising, a defining moment in modern Greek history. But the coronavirus pandemic changed things.
Greece registered a further 2,198 cases and 58 deaths on Monday, its second highest daily death toll so far.
Greece fared better than other European countries in the first wave of the pandemic last spring due to an early lockdown. But a surge in cases since early October has forced authorities to impose a second, nationwide lockdown which expires at the end of November.
Public gatherings of more than four people are banned until Nov. 18, according to police, and violators face fines of up to 5,000 euros ($5,928).
More than 5,000 police were deployed in central Athens on Tuesday while a helicopter hovered overhead through the day.