Reports from Belgian media say a blast was heard coming from Rue de Loi in Wetstraat.
People in neighbouring buildings have reported hearing the blast on social media.
The incident took place not far from Maelbeek station, where 15 people are believed to have been killed in a terrorist attack.
Suicide blasts at Zaventem airport in Brussels have also killed 13 people, according to the latest reports.
More to follow…
A policebomb squad are said to have been at the scene and detonated the suspected device in a controlled explosion.