Later, the victims' Swedish nationality was confirmed by Belgium's prime minister. The threat of terrorism in Brussels has reached its maximum point.
According to Uefa, the football match between Belgium and Sweden that was taking place in the city has been called off.
The shooter ran away and is still at large. Authorities claim to be treating the shooting as an act of terrorism.
An Arabic-speaking individual who claimed to have carried out the act in the name of God was seen on social media posting a video.
The actor said he had killed three individuals in the video. Although the Federal Prosecutor's office has acknowledged seeing the footage, it is unable to confirm that he is the shooter.
The police, according to information provided to the BBC, are verifying the attack's video and other available material.
Following the shooting on the Boulevard d'Ypres, federal prosecutors in Belgium have since informed the AFP news agency that a terrorism investigation has been launched.
A man in a bright jacket gets off a scooter while carrying what appears to be an assault-style weapon, according to a social media video posted by the daily Het Laatste Nieuws on Monday but unconfirmed by BBC News. He then enters a nearby glass-fronted business.
Then, he seems to shoot at least one victim.
Following the incident, which occurred at approximately 19:00 local time (17:00 GMT; 18:00 BST), police and emergency personnel have closed neighboring roadways.
The Swedish Prime Minister has been sent my profound sympathies in light of tonight's horrific incident in Brussels on Swedish nationals, Belgian Prime Minister Alexander de Croo wrote on X, formerly Twitter.
"Our hearts go out to the friends and family who lost a dear one. The war against terrorism is a cooperative effort amongst close allies.
Whether the victims were in Brussels to watch their national team play is not yet known.
BBC