Explosions tore through the departure hall of Brussels airport on Tuesday morning killing up to 13 people and injuring 35 others and a second blast struck a metro station in the capital shortly afterwards, killing 15 people and injuring 55 others, reports AFP.

The Belga agency said shots were fired and there were shouts in Arabic shortly before the blasts at the airport. Pictures on social media showed smoke rising from the terminal building through shattered windows and passengers running away down a slipway, some still hauling their bags.

The blasts at the airport and metro station 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.

British Sky News television's Alex Rossi, at the airport, said he heard two "very, very loud explosions".

The agency had then cited hospital sources as saying up to ten people were killed at the airport.

Belgian Prime Minister Charles Michel said on his twitter feed: "We are following the situation minute by minute. Our priority concern is for the victims and those present in the airport."

Brussels airport said it had cancelled all flights and the complex had been evacuated and trains to the airport had been stopped. Passengers were taken to coaches from the terminal that would remove them to a secure area.