Several explosions have struck Brussels airport and the metro system, causing at least 13 deaths, Belgian media report.
Two blasts tore through the departures area of Zaventem airport shortly after 08:00 local time (07:00 GMT).
An hour later, an explosion hit Maalbeek metro station, close to the EU institutions. The airport and whole transport system have been closed.
The attacks come four days after Salah Abdeslam, the main fugitive in the Paris attacks, was seized in Brussels.
The Belgian government has confirmed casualties at the airport but has given no numbers. The cause of the explosions is unknown.
Belgium has now raised its terror threat to its highest level.
Belgian broadcaster VRT said that in addition to the dead at the airport, at least 35 people were severely injured.
The Belga news agency reports that shots were fired and shouts in Arabic were heard before the two explosions. Some reports say it was a suicide attack.