Brussels is at its highest level of terror alert after a warning that an attack like that seen in Paris is “imminent”, forcing the closure of the city’s Metro.
The Belgian capital’s underground transport system will be closed until Sunday afternoon, dozens of events have been cancelled and many public places closed, the government has said.
Belgium’s Prime Minister said the terror alert was as a result of “quite precise information about the risk of an attack like the one that happened in Paris”.
Heavily armed soldiers and police are patrolling the city amid fears at least one suspect in the Paris attacks could be in Belgium.
Belgian PM Charles Michel said the government would review the security situation towards the end of the weekend.
It comes after a meeting of top ministers, police and security services in the city, which is also home to the European Union and NATO headquarters.
A spokesman for the country’s crisis centre said in a statement: “Following our latest evaluation… the centre has raised its terror alert to level 4, signifying a very serious threat, for the Brussels region.
“The analysis shows a serious and imminent threat requiring specific security measures as well as detailed recommendations to the population.”
The rest of the country, outside Brussels and the Vilvoorde area, remains at level 3, meaning an attack is probable.
Sky’s Enda Brady, who has arrived at the main Bruxelles Midi train station, said: “Extraordinary security scenes here. Soldiers from the Belgian army carrying assault rifles… in groups of four up and down the main concourse and on platforms.
“It’s a totally surreal atmosphere. It’s just extremely quiet. It’s normally a very very busy station, especially at weekends. Belgian police also heavily armed. Everyone knows what’s going on…”
Belgium, and Brussels in particular, have been at the centre of investigations into the Paris attacks after it emerged that two of the suicide bombers had been living in the country.
Three people detained in Brussels are facing terrorism charges.
he brother of one of the suicide bombers, who was also living in Brussels, is still on the run.
Salah Abdeslam was briefly pulled over by French police near the Belgian border last Saturday morning along with two of those in custody.
The Federal Prosecutors Office in Brussels said on Saturday that police had searched the house of a person who was arrested on Friday and had found “a few weapons”.
The last time any part of the country was put on maximum alert was in May 2014 when a gunman shot dead four people at the Jewish Museum in Brussels.