At least 14 people died and 92 were wounded in the twin blasts, and some 20 people were killed and 106 injured – 10 critically – in the metro explosion.
Belgium’s federal prosecutor said all three explosions were “terrorist attacks”.
“There were two explosions in the departure area, one probably caused by a suicide bomber,” said Frederic Van Leeuw of the airport attack.
Police recovered a Kalashnikov assault rifle next to the dead attacker. An unexploded bomb belt was also reportedly found at the terminal.
There was a controlled explosion of a suspect package at the Vrije University in central Brussels – as the country’s Tihange nuclear power plant was evacuated.
Two people were arrested by armed police at the city’s Noord railway station hours later – as officials said they feared “people are still at large”.