BRUSSELS, Dec. 16 (Xinhua) -- Thousands of protestors clashed with police during march against a UN migration pact here on Sunday, while a peaceful counter-protest in favour of the pact drew over 1,000 people on the same day.

The march against the Untied Nations Global Compact for Migration, signed in Marrakech last week, was triggered by Flemish right-wing parties amid fears the pact could lead to an increase in immigration.

Police were forced to deploy tear gas and water cannon as clashes broke out near the European Union institution quarters.

It has been reported that, overall about 5,500 protesters took part in both marches.

The Brussels prosecutor's office has also confirmed that a hundred people were arrested, including the judicial arrest of six people in connection with the damage caused to EU buildings, acts of armed rebellion and drug offences.

A counter-protest organised by left-wing groups and charities in the city centre was held peacefully.

The largest member of Belgium's ruling coalition, the right-wing N-VA party, left the government last Sunday in protest against the prime minister's decision to sign the agreement.

In July, 196 UN members agreed the Global Compact for Safe, Orderly and Regular Migration.

It was signed by 164 countries in Marrakech last week, with the U.S. and a number of European countries refusing to formally adopt it.

The deal, which is not legally binding, seeks a common approach to international migration to optimize the overall benefits of migration, while addressing its risks and challenges for individuals and communities in countries of origin, transit and destination.