The courthouse of Verviers in the Liège province was shot at on Wednesday night.
A bullet damaged a window and ended up in the office of one of the judges, according to the public prosecutor, confirming earlier reports in L'Avénir.
"On Thursday morning, employees discovered that a window near the entrance door was damaged by a gunshot," said an attorney, who emphasised that the case is being taken very seriously, reports Het Laatste Nieuws.
"This is the first time that we are confronted by a situation like this, and that the judicial institute has been attacked," the public prosecutor's office added.
It is not yet clear whether or not there is a connection with one of the cases of the judge whose office the bullet hit.
Maïthé Chini
The Brussels Times