The suspected maker of bombs used during the massacre in Paris last November, he is now being hunted over the central role he is thought to have played in killing at least 34 people in the Belgian capital.
Laachraoui is believed to be the third man pictured in a CCTV image taken at Brussels airport moments before the attacks, said Belgian newspaper La Derniere Heure.
Wearing a black hat, an off-white jacket over a white shirt and pushing a baggage trolley, he is believed to have left the “biggest explosive charge” at the scene.
Media reports that he had been arrested in Anderlecht on Wednesday were denied by Belgian prosecutor Frederic Van Leeuw, who said yesterday the third suspect’s bomb “did not explode” and he was still at large. He did not formally identify him as Laachraoui.
Authorities had already been searching for the 24-year-old in connection with suspected Paris attacker Salah Abdeslam, who was arrested just four days before the Brussels bombings.
Earlier this week, Belgian prosecutors said DNA evidence had identified the Belgian as being one of the accomplices of Abdeslam in the Paris attacks which killed 130 people.
His DNA was said to have been found on “several explosive belts”.