Farmers from the Dutch-speaking Flanders region gathered at Brussels' central Arts-Loi street and blocked roads in response to calls from unions.
They chanted slogans against the Flanders regional government's plan to limit nitrogen emissions by 2025, carrying banners that read: "No farmers, no food and no future."
Protesters demanded the government reverse the plan, otherwise they will not be able to continue in agriculture and livestock which would drive them into a crisis.
Meanwhile, police had advised the public not to drive to the city via cars and to use public transportation.
The European Commission did not release funds to farmers in the region under the EU's Common Agricultural Policy because it did not find the regional government's reduction measures sufficient.