Around 30,000 people marched through Brussels on October 9 in a national strike against planned government budget cuts, Reuters reported. The main march passed off peacefully, but a few dozen masked protesters dressed in black broke away and clashed with police near Brussels Central Station.

The splinter group threw rocks, bottles, bricks, stones and fireworks at officers, set fires including on buses, and damaged public property. Police responded with water cannon and tear gas. Twenty-one people were detained or arrested, including 13 minors.

The strike was called by Belgium’s two largest unions, the socialist FGTB/ABVV and the Christian CSC/ACV. The unions say the budget measures would make workers, pensioners and low-income households bear the burden of deficit reduction.

Students joined the march, some carrying placards reading “I skipped class to defend class”. Public transport and air travel were disrupted, and many schools and childcare facilities were affected. The unrest follows days of student protests in Liege, where local media reported 107 arrests.

The Belgian walkout is part of a wave of protests sweeping Europe over education funding and austerity.