A police officer was injured during a house raid in the southern suburb of Forest, though it was unclear whether he was hit by gunfire, a police spokeswoman said, as cited by Reuters.
She declined to comment on reports that counter-terrorism units were involved in the search.
La Dernière Heure newspaper reported that a Kalashnikov was the gun used in the shooting, and that the shooter is on the loose.
The mayor of the municipality, Marc John Ghyssels, confirmed the shooting to Le Soir newspaper, but said the number of suspects on the run has not yet been determined.
Belgian authorities are still on the hunt for suspects and associates linked to the Brussels-based terrorists responsible for the attacks in Paris on November 13, which killed 130 people.