Police used water cannon and teargas after coming under attack from football supporters who brought havoc to the centre of Brussels on Sunday following Morocco's shock 2-0 World Cup win over Belgium in Qatar.
Dozens of fans smashed shop windows, threw fireworks and torched vehicles.
Even before the end of the match, "dozens of people, including some wearing hoodies, sought confrontation with the police, which compromised public safety," Brussels police said in a statement.
A spokeswoman said some fans were armed with sticks and a journalist "was injured in the face by fireworks".
Around a hundred police officers were mobilised while residents were warned to avoid certain areas of the city centre. Metro stations were closed and streets sealed off to limit the spread of the violence.
Belgium is home to around 500,000 people of Moroccan descent.