Two of the suicide bombers who carried out attacks in Brussels onTuesday have been named as brothers Khalid and Brahim el-Bakraoui, Belgian nationals.
The federal prosecutor said Brahim was part of the attack at Zaventem airport that killed 11 people. Khalid struck at Maelbeek metro, where 20 people died.
Two other attackers at the airport have not yet been identified. One of them died, another is on the run.
So-called Islamic State (IS) has said it was behind the attacks.
Belgium is observing three days of national mourning. The nation held a minute's silence at midday (11:00 GMT) on Wednesday. Belgium's king and queen visited the airport and met some of the 260 injured in hospital.