Reports by broadcaster VRT say that the threat was made through a telephone call in English, with a parliamentary clerk alerting Homans.
Multiple reports on Flemish media say the phone call could be linked to an event in celebration of the 40th anniversary of a Kurdish institute, which was supposed to take place in the building this afternoon but has since been cancelled.
The Kurdish Institute in Brussels did not immediately reply to a request for comment.
Police cleared the building shortly before 3:00 PM, according to a tweet in the official account of the Flemish parliament.
Als gevolg van een bommelding zijn de gebouwen van het @vlaparl ontruimd. Alle activiteiten voor vandaag zijn opgeschort tot nader te bepalen datum.