Tens of thousands of people demonstrated through central Brussels on Sunday in protest at reinforced Covid-19 restrictions imposed by the Belgian government to counter the latest spike in coronavirus cases.
Many among the estimated 35,000 people at the rally had already left for home when the demonstration descended into violence.
Several hundred people started pelting police, smashing cars and setting rubbish bins ablaze.
Police responded with tear gas and water cannons and sought to restore order as dusk settled on the city.
Three police officials and one demonstrator were injured in the clashes.
In addition, 42 protesters were detained and two were arrested and charged over the violence that followed the march, said police spokesman Ilse Vande Keere.
The marchers were protesting against the government’s strong advice to get vaccinated and any possible moves to impose mandatory jabs.
Shouting “Freedom! Freedom! Freedom!” and singing the anti-fascist song Bella Ciao, protesters lined up behind a huge banner saying “Together for Freedom” and marched to the European Union headquarters.
Amid the crowd, the signs varied from far-right insignia to the rainbow flags of the LGBT community.
The World Health Organisation said last week that Europe was the hotspot of the pandemic, the only region in which Covid-19 deaths were rising.
The autumn surge of infections is overwhelming hospitals in many central and eastern European nations, including Ukraine, Russia, Romania, the Czech Republic and Slovakia.
In the past days there have been many anti-vaccination marches in Europe as one government after another tightened measures.
Dutch police arrested more than 30 people during unrest in The Hague and other towns in the Netherlands on Saturday, following much worse violence the previous night.
Austria is entering a 10-day national lockdown on Monday for everyone, after first imposing a lockdown on the unvaccinated.
Christmas markets in Vienna were packed on Sunday with local people and tourists taking in the holiday sights before shops and food stalls are forced to close.