Belgium on Saturday charged a suspect thought to be the fugitive third Brussels airport bomber with terrorist murder, as a peace march for the victims was cancelled for security reasons after the attacks in the heart of Europe.
The postponement of the Easter Sunday rally underscored the tension in Belgium as police track members of an Islamic State group cell linked to both Tuesday's Brussels attacks that killed 31 people and a similar assault on Paris in November.
The airport suspect officially identified as Faycal C and named by local media as freelance journalist Faycal Cheffou was arrested on Thursday night and investigators believe he could be the man pictured in airport surveillance footage alongside two other suicide bombers.
The third bomber, wearing a distinctive dark hat and white jacket, has been the subject of a massive manhunt after his device failed to go off in the attack at Zaventem airport.
Brussels airport said it will not reopen before Tuesday at the earliest as it implements new security measures and repairs the departure hall wrecked by the bombers, believed to be from the Islamic State group.
A march had been planned on Sunday from the central Place de La Bourse, which has become a shrine to the victims, but it was cancelled after authorities said it could draw much-needed resources away from the investigation.
"Let us allow the security services to do their work and that the march, which we too want to take part in, be delayed for several weeks," Brussels mayor Yvan Mayeur said.
March organisers said the "security of our citizens is an absolute priority. We join the authorities in proposing a delay and ask people not to come this Sunday."
Ministers insist they did everything possible to prevent Tuesday's attacks and track a network also linked to November's Paris attacks, but the Belgian government is facing a torrent of criticism at home and abroad.
Many believe it failed to do enough to stop young Belgian fighters going to Syria, and two senior ministers have offered to resign after it emerged airport bomber Ibrahim El Bakraoui had been deported from Turkey as a "terrorist fighter".
"It is an endless nightmare for a country turned upside down," said Le Soir daily in a front-page editorial.
Pop diva Mariah Carey on Friday cancelled a show in Brussels, saying she was advised to do so "for the safety of my fans, my band, crew and everyone involved with the tour."
In contrast, veteran French rock star Johnny Hallyday was going ahead with two planned concerts in Brussels over the weekend.
Heavily armed soldiers and police patrolled Brussels and the airport on Saturday, underlining the tense atmosphere in the city that is home to the EU and NATO headquarters.
Prosecutors on Saturday charged three people including Faycal C, who is the first person formally accused over the suicide attacks on the airport and the Maalbeek metro station.
He was arrested on Thursday night outside the federal prosecutor's office with three other people and "has been charged with taking part in a terrorist group, terrorist murder and attempted terrorist murder," the prosecutor said.
Asked if he was the suspected third bomber dubbed the "man in the hat" alongside bombers Ibrahim El Bakraoui and Najim Laachraoui, a source close to the inquiry told AFP: "That is a hypothesis the investigators are working on."
Another man arrested in Belgium named as Rabah N. was also charged Saturday over a new plot to hit Paris, deepening the connections in what French President Francois Hollande has described as a single terror cell straddling both France and Belgium.
French police said Friday they had foiled a terror strike in France by 34-year-old Reda Kriket - previously convicted in Belgium in a terror case alongside Paris attacks ringleader Abdelhamid Abaaoud - and discovered explosives at his home.
A third man, Aboubakar A, was charged with taking part in terrorist activities but prosecutors gave no further details.
A suspect shot in the leg Friday at a tram stop in the Schaerbeek district of Brussels is being held for another 24 hours as investigations into the French plot continue.
The Franco-Belgian links deepened on Friday when it emerged airport attacker Laachraoui's DNA was found on bombs at the Bataclan concert hall and Stade de France sites in the Paris attacks.
Belgium's ageing nuclear power plants meanwhile came under scrutiny as a possible terror risk, with the EU's anti-terror chief Gilles de Kerchove telling La Libre Belgique newspaper they face the threat of a terrorist cyber-attack over the next five years.
Prosecutors confirmed Saturday that a security guard at a medical research facility that used radioactive isotopes had been murdered in Thursday but denied there was any terror link.
Officials said Saturday that 24 of the victims from Tuesday's attacks have been formally identified and 101 injured people are still in hospital.