The RIOTERs set fire to cars and threw rockets at the cops to mark the tenth anniversary of a murder of "police brutality".
Hundreds of protesters marched through Athens in homage to fifteen year old Alexandros Grigoropoulos, who was killed by some officers in 2008.
Riot police were forced to assault the Exarchia district with batons and tear gas after demonstrators started throwing petrol bombs and fireworks.
More than two thousand policemen were deployed to help create a steel ring around sensitive points, while a helicopter circled the sky.
The bins and cars were burned while the huge crowd made their way through the city.
Clashes also erupted during demonstrations in the northern city of Thessaloniki, with police firing tear gas and stun grenades at demonstrators after being targeted with stones and petrol bombs.
In 2008 thousands of people took to the streets after Grigoropoulos was hit.
The carnage has marked the worst clashes in Greece in recent decades.
The girl, 14, "raped and killed by a boy, 16, had the DNA of her stepfather on underwear"
HORROR WITHOUT HEAD
Toddler, 1, beheaded after the scarf got tangled in the wheels of the bike
The former glamor model took drunk driving after having "struggled" over the end of her career
The mother who treated the child as a "fashion accessory" in a cage after the death of 41 wounded
GIVE TO THE NAME
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The policemen fought for weeks to regain control, with thousands of protestors fueled by anger over unemployment and economic hardship.
It comes after the demonstrators in France – wearing their signature yellow jackets – have promised to carry on their violent anti-government demonstrations, as part of a "revolution".
Far-right groups want to exploit the widespread rage against President Macron to help overthrow the "system" in a "smash and kill mission".
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