Belgian soldiers patrol at Zaventem international airport near Brussels, November 21, 2015, after security was tightened in Belgium following the fatal attacks in Paris. [Photo/Agencies]

BRUSSELS - Belgian security officials were set to review on Sunday whether to keep Brussels on maximum alert, leaving the public to wonder whether the blanket metro closure and cancellation of events could continue into the working week.

Prime Minister Charles Michel has advised the public to be alert rather than panic-stricken, but also said the raised security level on Saturday was due to the "serious and imminent" threat of Paris-style coordinated attacks.

Belgium's crisis centre, a body that advises the government on security measures, said on Sunday the alert status remained at four, the highest level, for Brussels, with the rest of the country on three, meaning a possible and probable threat.

Intelligence, police and judicial officials would review the status during the course of the day. The national security council, including top ministers, was expected to convene on Sunday afternoon to determine what measures to take or retain.

Belgium has advised the public to avoid crowds in the capital, and closed the metro system, museums, cinemas and shopping centres. Clubs and venues have cancelled events.

That said, Brussels on Sunday morning resembled most other Sundays, with the normal limited number of shops, such bakeries and small supermarkets open, and many churches in the largely Catholic country still holding services.

However, larger markets were shut.

Belgium has been at the heart of investigations into the Paris attacks after links to Brussels, and the poor district of Molenbeek in particular, emerged.

Two of the Paris suicide bombers, Brahim Abdeslam and Bilal Hadfi, had been living in Belgium. Fugitive suspected militant Salah Abdeslam, Brahim's 26 year-old brother, slipped back home to Brussels from Paris shortly after the attacks.