An Islamic State flag was found by the body of a gunman shot in a house raid near Brussels, authorities said.
Two suspects escaped during the anti-terrorism raid, which was linked to the Paris attacks.
Two suspects in the raids in Brussels are still at large after one was "neutralised", local media has reported.
Armed officers launched a manhunt on the streets of the Forest district after at least one gunman opened fire through the door of an apartment, as police carried out a raid linked to November's terror attacks in Paris.
At least one of the suspects still at large is believed to have barricaded themselves inside the apartment.
Local media reported that a police helicopter spotted another suspect, armed with a machine gun, in a nearby garden before he was "neutralised" by security forces.
The reports do not clarify whether "neutralised" means killed or arrested.
Belgian police carried out the raid with the support of their French counterparts. Four officers were injured during the exchange of bullets.
A large part of southern Forest has been cordoned off and residents asked to stay indoors, while two schools have been placed on lockdown while the search continues.
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.