A week after Paris bombings and shootings carried out by Islamic State militants, of whom one suspect from Brussels is at large, Brussels was placed on the top level "four" in the government's threat scale after a meeting of police, justice and intelligence officials.
Soldiers were on guard in parts of Brussels, a city of 1.2 million people and home to institutions of the European Union and the headquarters of NATO.
"The result of relatively precise information pointed to the risk of an attack along the lines of what took take place in Paris," Prime Minister Charles Michel told a news conference on Saturday after a meeting of the national security council. The Paris attacks left 130 people dead.
"We are talking about the threat that several individuals with arms and explosives would launch an attack perhaps in several locations at the same time," Michel said, adding people should be alert but not panic.
He declined to elaborate, but said the government would review the situation on Sunday afternoon.
The metro system is to remain closed until then, in line with recommendation of the government's crisis center. Major shopping centers and stores did open on Saturday morning, with soldiers deployed outside shops.
However, many began closing their doors from around midday.
I'm not terribly surprised by this, given the connection to Brussels by the militants who hit Paris eight days ago, the Belgian capital seemed like the obvious next target in Europe. I'm hoping that nobody else is hurt and that Belgian police can find these guys before they strike.