At least 10 people have been killed and several injured after two explosions ripped through Zaventem Airport in Brussels.
The country's public broadcaster RTBF said there were up to 10 people dead and a further 30 wounded.
Explosions At Brussels Airport:
Video and images on social media showed smoke rising from an airport building and shattered windows.
Confused and shocked passengers fled the terminal to safety as they were evacuated by armed police.
Footage also showed ceiling tiles littered across the floor and strewn black luggage belts, cases and bags at a check-in desk.
According to reports the suspected terror attack centred on an American Airlines desk in a departure hall at around 8am.
Airport spokeswoman Anke Fransen said: "There were two blasts in the departure hall. First aid team are in place for help."
A police official added: "One person has died and perhaps there are several more."
The attack comes as the Belgian capital is on high alert following the dramatic arrest of Paris attacks suspect Salah Abdeslam in the city last Friday.
Sky's Alex Rossi, at the scene, said: "I was in the duty free in Zaventem Airport and I heard two very, very loud explosions.
"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 although that hasn't been verified by any of the authorities here at the airport.
"Don't know how the explosion took place, the method if you like. But it certainly seems Brussels airport has been targeted in a terrorist attack.
"We are all being moved out of the airport now towards the emergency exit.
"There is a great deal of confusion here. Certainly there are a number of very upset, as you might imagine, very frightened people."
He added: "There are fears that there might be other attackers."
Eurostar services - and all trains to the airport have been suspended which has been closed until further notice.
The city's metro stations were also shut as Belgium hiked its terror threat to its highest level following the apparent coordinated attacks.
UPDATE: It is now known that the airport explosion's were suicide attacks. Both the airport and Metro station attacks were timed to coincide at about 8pm Belgium time.