Several metro stations in Brussels were closed on Wednesday after a shooting at the central Clemenceau station, the Belgian prosecutor's office said.
No injuries were reported, it said.
The suspects fled into the metro tunnels afterwards, a source close to the investigation said, adding that police were looking for two suspects.
Sources close to the investigation told local media the incident may have been drug-related.
Images on VRT's website showed two people walking into the station and opening fire. The images could not immediately be verified by Reuters.

Ringleader of Wagner-directed UK arson on Ukrainian business jailed
Britain pushes allies to boost Ukraine support as Zelenskyy lands in London
Erdogan says US, others must press Israel to abide by Gaza ceasefire
EU vows financial backing for Kyiv
