Two suicide bombers behind the Brussels attack on Tuesday were identified as brothers and Belgian nationals.
Khalid and Brahim el-Bakraoui are responsible for the Zaventem airport attack that killed 11 people and Maelbeek metro that claimed 20 others.
Two other attackers are still to be identified, while one died during the bombings and the other is still on the run.
According to foreign media one of the brothers, Brahim, has left a note with his description.
Belgium is observing three days of national mourning.