The metro system in Brussels has been closed due to what officials have described as a “serious and imminent threat.”
At four, Belgium is on its highest level of alert.
People are being warned to avoid crowds because of a “serious and imminent” threat.
More soldiers and police have already been deployed in the wake of the Paris attacks, including in the city’s iconic Grand Place.
French national Salah Abdeslam, whose brother blew himself up in the French capital, remains at large and is the subject of an international arrest warrant.