At least 21 have died following explosions at Brussels airport and a metro station, local media has reported.
The European Union’s political heart was on high alert after an explosion at metro stations near the 28-member bloc’s main buildings in Brussels.
The European Commission’s vice-president Kristalina Georgieva said meetings were cancelled and urged people to “stay home or inside buildings” following reports of an explosion at Maelbeek station.
The metro station is close to the commission’s Berlaymont headquarters, the European Parliament and the European Council’s Justus Lipsius building in the Belgian capital.
Ms Georgieva said on Twitter: “Following situation in Brussels. EU institutions working together to ensure security of staff& premises.Please stay home or inside buildings.
“All EU institutions are at alert level ORANGE – all meetings on premises and outside cancelled, access only for staff with badges.”
A European Council tweet said: “Closely monitoring the situation. All meetings cancelled this morning. Priority to ensure safety of staff & visitors.”