About 10 protesters gathered in the centre of Brussels on Sunday. They were encircled by police forces. Several people were detained.
The police mobilized an equestrian patrol, several special forces minibuses and officers with police dogs to secure the scene.
Earlier in the week, one of the Flemish nationalist groups said it was planning to hold a "March on Brussels" on Sunday, but the authorities banned the event to prevent unrest.
According to the Brussels Times, counter-demonstrations organised by left-wing and anti-fascist groups were also banned, in line with police recommendations. Last year, a demonstration against a UN Pact on Migration called "March against Morocco" was allowed by Belgium's Council of State and saw violent clashes between protesters and police.