Belgian and French authorities continued a manhunt for at least two suspects believed directly linked to the killings in Paris.
About half of all subway stations in Brussels were operating for the first time since the weekend. Despite the easing of restrictions, Brussels home to the European Union and NATO headquarters remained under the highest alert level due to what authorities have described as a serious and imminent threat of attack.
The threat alert level is expected to remain at that level until at least Monday, barring a major development such as the arrest of suspects in the Paris attacks.
The Belgian government has also ordered health and emergency services to take precautionary measures to ensure their services aren't infiltrated by extremists.
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"We have to be sure that we can see everybody has an identification badge," Health Minister Maggie De Block told VRT network. "When ambulances arrive, we have to see from where they come, who is in it. Really as a precaution."
"There were indications that there would be attacks on Sunday evening and they did not materialize," Jambon said, adding that otherwise "you don't impose terror level 4," the highest possible.
The minister refused to elaborate what kind of attacks the government believed had been planned.
The reopening of schools and some subway stations restored a sense of normality to Brussels, parts of which have been deserted for days.
In the stunned city, home to the European Union and NATO,
mourners returned to the Place de la Bourse square where they stood silently under umbrellas, some in tears and others still in shock.
"The government knows a lot but they do nothing. Why didn't they do something to stop this attack? I think the government is a bit to blame for this situation," said Sergio Jorge de Oliveira Silva Lima, 38, a Portuguese citizen who has lived in Belgium for 15 years.
A huge manhunt is still under way for at least two suspects -- one of the airport attackers wearing a hat whose bomb failed to go off and another man seen in the metro with the bomber there.
Prosecutors have confirmed that Khalid El Bakraoui -- who blew himself up at Maalbeek metro station shortly after his brother Ibrahim did the same at Zaventem airport -- was the subject of an international warrant over the Paris attacks.
Investigators also say he rented an apartment in Brussels used by key Paris suspect Salah Abdeslam, who was arrested in the Belgian capital last week.
The brothers were also listed in American terrorism databases, television network NBC reported.
Belgium has lowered its terror alert to the second-highest level for the first time since the attacks, but the police and military presence on the streets of the capital remains high.
Harrowing stories continued to emerge from survivors of the attacks, in which people of around 40 nationalities were killed or wounded.
Brazilian professional basketball player Sebastien Bellin said that as he lay bleeding profusely and fearing death at Brussels airport, he thought of something odd: his daughter's tennis skills.
"I just didn't want my girls to grow up without a dad, you know?" Bellin, 37, told US network ABC from his hospital bed.