Belgium’s Prime Minister, Alexander De Croo, confirmed Swedish citizens were among the victims of the shooting.
Mr De Croo and his interior minister, Annelies Verlinden, were reported to have arrived at the centre following the attack.
The prime minister said: “My most sincere condolences to the loved ones of the victims of the cowardly attack in Brussels.
“We are monitoring the situation and asking Brussels residents to be vigilant.”
Hadja Lahbib, Belgium’s foreign minister, confirmed the incident as a terror attack. She tweeted: “Horrified by the terrorist attack which left two victims in the heart of Brussels. All necessary means must be mobilized to combat radicalism. Thoughts for the victims, their loved ones and for our law enforcement.”
Ursula von der Leyen, the European Commission’s president, said: “My heart goes out this evening to the families of the two victims of the despicable attack which took place in Brussels.
“My absolute support for the Belgian police forces, to quickly apprehend the suspect.
“We are united against terror.”