Belgium is observing three days of mourning following bomb attacks in the capital Brussels that left 34 people dead and about 250 wounded.
A minute's silence for the victims will be held at midday (11:00 GMT).
Police are continuing a huge manhunt for a suspect caught on CCTV shortly before two bombs exploded at Zaventem airport on Tuesday morning.
An hour later another blast tore through a metro train near the Maelbeek station.
So-called Islamic State (IS) has said it was behind the attacks and warned that more would follow.