Police closed down a street in the Forest neighbourhood in a major security operation involving specialist armed units on Thursday.
Armed police officers were pictured hiding behind buildings and staking out a building rooftop in the neighborhood of the Belgian capital on Thursday.
A police helicopter flew overhead.
Belgian media said an armed person may be hiding in a building.
Police were not immediately available to comment on the incident, which began around lunchtime.
Broadcaster RTL quoted Forest mayor Marc-Jean Ghyssels as saying that police 'suspect the presence of an armed man.'
Witnesses at the scene told local media that armed police at the scene are ready to fire.
'I was behind a bus when all of a sudden, the police came armed, they told us to leave the street,' one told RTBF.
'So I went around and there I saw people start running in all directions.'
Another told RTBF that officers warned residents to stay in the homes.
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