A police operation is under way in central Brussels, with residents being told to stay away from their windows, Belgian broadcaster RTL reported.
The broadcaster said police were carrying out an operation near the Rue du Midi, a few blocks from the Grand-Place, the city’s central square.
One eyewitness told RTL they were dining in a restaurant when police told them to finish their meal and wait at the door for the signal to leave.
Other eyewitnesses took to Twitter to post photos appearing to show a police security perimeter set up.
“Police and military ask us to stay in the hotel,” one tourist tweeted.