Police hunt third suspect whose bomb failed to detonate inside airport

Belgian officials have confirmed a third bomb that failed to explode was discovered in the main hall of Brussels' airport, where two blasts killed dozens of people on Tuesday night.

"Three bombs were brought into the building, of which one failed to explode," Lodewijk De Witte, the governor of Flemish Brabant province, told a press conference at the airport.

An army team later blew up a third unexploded suspect package at the shuttered airport.

Belgian authorities released pictures of two of the suspected suicide attackers calmly pushing trollies through the terminal and said they were "actively searching" for a third whose bomb failed to go off.

Witnesses described horrific scenes at the airport, with victims lying in pools of blood, their limbs blown off.

There were chaotic scenes as passengers fled in panic, and plumes of dark smoke could be seen rising from holes punched through the roof of the building by the blasts.

"A man shouted a few words in Arabic and then I heard a huge blast," airport baggage security officer Alphonse Lyoura told AFP.

"A lot of people lost limbs. One man had lost both legs and there was a policeman with a totally mangled leg."