The two suicide bombers who carried out the Brussels Airport attacks were brothers Khalid and Brahim El Bakraoui.<br />Both brothers were known to police and had criminal records.<br />A third man pictured with them at the airport is still being sought.<br />Khalid, under a false name, had rented the flat in the Forest borough of the Belgian capital where police killed a gunman in a raid last week, RTBF said.<br />After the raid, investigators found an Islamic State flag, an assault rifle, detonators and a fingerprint of Paris attacks prime suspect Salah Abdeslam, who was arrested three days later.<br />Belgium has declared three days of mourning after bomb attacks ripped through the capital's airport and the Maelbeek underground train station, killing 34, with Islamic State claiming responsibility.