Tension erupted outside the Commission building during the march
Thousands of protesters marched on the UN Global Compact on Migration, overshadowing a smaller demonstration in support of the agreement, which was signed by the Belgian government last week.
Tension erupted outside the Commission building during the march. Police used tear gas and water cannons to evacuate the area.
The police claims that about 5.500 people marched in the biggest protest of the Flemish right nationalist parties in that part of the capital which established the main EU institutions.
A separate anti-demonstration with the participation of about 1.000 people, organized by leftist organizations and NGOs, took place in the center of the capital, according to the APE-MPE.
The Flemish Nationalist Party (N-VA), the largest party in parliament, withdrew its ministers from the ruling coalition last week after Prime Minister Charles Michel refused to comply with his request not to sign the Marrakesh Pact. .
Michel had secured a large parliamentary majority in order to maintain Belgian support for the UN Pact by securing the support of the opposition Socialists and the Greens. Analysts say the N-VA move was the warning shot for a campaign ahead of the May federal election.
The UN Pact was agreed in July by all 193 UN members, except the United States, but only 164 formally signed it at the Marrakesh Immigration Summit last week.
It has come under fire from European politicians, who say it will increase immigration to Europe as the bloc becomes increasingly reluctant to accept refugees and migrants following the 2015 boom in arrivals.
Ten countries, most notably the former communist Eastern Europe, have withdrawn from the non-binding Pact.
With a record 21,3 million refugees worldwide, the United Nations began working on the Pact after more than one million people arrived in Europe in 2015, many of whom had fled Syria to escape the war, or Africa to escape extreme poverty.