Tens of thousands of people have been marching in the Belgian capital, Brussels, to protest against anti-Covid measures.
Some protesters threw fireworks at police officers, who intervened with tear gas and water cannon.
Demonstrators are mainly opposed to the use of Covid passes, which stops the unvaccinated from entering venues such as restaurants or bars.
This comes after fresh protests in the Netherlands against new lockdown rules.
On Saturday, people hurled fireworks at police and set fire to bicycles in The Hague, one night after protests in Rotterdam turned violent and police fired gunshots.
Thousands of demonstrators also took to the streets in Austria, Croatia and Italy as anger mounted over new curbs.
In Belgium, rules on face masks have been tightened, including in places such as restaurants where Covid passes are already required, and most Belgians will also have to work from home four days a week until mid-December. There are also plans to make vaccinations for health workers compulsory.
Earlier, the World Health Organization (WHO) said it was "very worried" about rising coronavirus cases on the continent.
Its regional director, Dr Hans Kluge, told the BBC that unless measures were tightened across Europe, half a million more deaths could be recorded by next spring.
"Covid-19 has become once again the number one cause of mortality in our region," he said, adding "we know what needs to be done" in order to fight the virus - such as getting vaccinated, wearing masks, and using Covid passes.
Many governments across the continent are bringing in new restrictions to try to tackle rising infections. A number of countries have recently reported record-high daily case numbers.