Pierre Meys, the spokesman for the Brussels fire brigade, told AFP 11 people died in twin blasts at Brussels airport.
There were also “around ten killed at the Maalbeek metro station where there was an enormous explosion,” he said.
“Most of the wounded have been evacuated. The scene is rather chaotic,” he said.
The blasts occurred four days after the arrest in Brussels of a suspected participant in November militant attacks in Paris that killed 130 people. Belgian police had been on alert for any reprisal action.
Video showed devastation inside the departure hall with items scattered across the floor.
Social media showed videos and pictures of smoke rising from the departure hall where windows had been shattered by the blasts.
Shots were fired shortly before the explosions, according to RTBF. Passengers were seen running away down a slipway.
Sky News’s Alex Rossi, at the scene, said he heard two ‘very, very loud explosions’. She said: “I could feel the building move. There was also dust and smoke as well.
“I went towards where the explosion came from and there were people coming out looking very dazed and shocked.
“The thinking here is that it is some kind of terrorist attack – that hasn’t been verified by any of the authorities here at the airport.”
All public transport has been shut down in Brussels and the government has asked all residents to remain where they are.
Security has also been reinforced at Paris and Frankfurt airports after the blasts, according to police.
An explosion at Brussels metro station close to EU institutions is being reported by Belgian broadcasters. (Courtesy Reuters and AFP)