A Brussels manhunt continued on Sunday in search of suspected Paris attacks fugitive Salah Abdeslam, who was thought to be armed with a suicide belt.
Belgium raised its terror alert on Saturday amid reports that Abdeslam was in the Brussels area and trying to get to Syria.
Belgium is believed to be a base for the Paris attackers - ISIS militants - who killed 130 people in Paris.
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.
The crisis center advised the public to avoid places with crowds, such as shopping centers, concerts, sports events or public transport hubs.
The city's museums and many cinemas and sports centers were shut, on separate orders from the city's 19 different local mayors. Clubs and venues canceled events, including a planned concert of veteran French rock singer Johnny Hallyday.
The agency has called on local authorities to postpone soccer matches, although most games in the top two divisions were set to go ahead.
Brussels-based Anderlecht's visit to Lokeren was canceled because the fixture was identified as a risk match requiring federal police, who were no longer available even with an increased military presence.
Foreign Minister Didier Reynders said that 1,000 troops were now available for patrols, double the level of a week earlier.
Stranded tourists on the cold and damp streets appeared more bemused than fearful, including Dutchman Gerrit Valkeman on a weekend trip with his wife.
"We had planned to visit museums, but are a bit puzzled about what to do now," he said at Place Royale, a square surrounded by museums and galleries.
Tour guide Stephane Bruno was planning to take a group of Americans around the city, but they canceled on advice from the U.S. embassy.
"My wife said not to go out today. But we were invaded by Napoleon and Louis XIV and were occupied eight times. We won't be defeated this time by terrorists," he said.
On normally bustling central shopping street Rue Neuve, Sofia Kostarako, a Greek national living in Brussels, said she had come out to show her sister Ioanna around.
"We will have a walk anyway. You can't change everything about your life. If something bad is to happen to you - it will," she said.