UPDATE: Serial blasts at the Brussels airport and the metro system have killed upto 23 people, the latest reports show. While Belgian authoritie confirmed 13 deaths so far, local media have reported almost two dozen people died in the coordinated attacks.
More than 30 people were wounded in multiple explosions at the Brussels airport and a metro station close to European Union institutions on Tuesday.
Belgium's public broadcaster VRT said the Brussels airport blast was a suicide attack.
An unknown number of people died in two explosions at the departure gate of the Zaventem airport.
Belgium's Belga news agency said there were shouts in Arabic before the blasts and shots were fired.
The deadly blasts happened four days after Belgian and French police conducted sweeping raids in Brussels in search of men involved in the Paris attacks in November and killed a suspected militant.
Belgian Prime Minister Charles Michel tweeted: "We are following the situation minute by minute. Our priority concern is for the victims and those present in the airport."
A TV journalist at the airport said he 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," said Alex Rossi of Sky News, according to Reuters.