Interpol has released a photo of a man the Brussels prosecutor said on Wednesday (March 23) was one of the Brussels suicide bombers who struck an airport terminal and a metro carriage in the city, killing at least 31.

Interpol named the man in the photo as Khalid El Bakraoui, whom prosecutor Frederic Van Leeuw said had blown himself up in the second carriage of a metro leaving Maelbeek station near the EU institutions on Tuesday morning.

His older brother Ibrahim was one of two bombers at Brussels airport, Van Leeuw said.

The other airport suicide bomber has yet to be identified, Van Leeuw told a news conference, and one man captured on CCTV at the airport as being with the two men is still on the run.

"The third suspect wearing a light jacket and a hat is on the run. He put down a large bag then left before the explosion. His bag contained the largest explosive charge. Shortly after the arrival of the bomb disposal unit, this bag blew up because of the highly unstable nature of the explosives. Fortunately, nobody was injured thanks to the professionalism of the forces involved. This third person, still unidentified, is being actively sought," Van Leeuw said.

At a raid in the Brussels district of Schaerbeek on Tuesday night police found 15kg of explosives, 150 litres of acetone, 30 litres of oxygenated water, detonators, a suitcase filled with screws and nails as well as materials, such as plastic boxes, needed to pack up the explosives.