Paris suspect Salah Abdeslam has been surrounded and wounded in an anti-terror police raid in Brussels, local media say.
This has not been officially confirmed. Shots were earlier heard in the Molenbeek area of Belgian's capital.
Belgian PM Charles Michel had to urgently leave an EU-Turkey summit in Brussels, a BBC reporter says.
Abdeslam is a key suspect in last year's Paris attacks in which 130 people died.
His fingerprints were found in a Brussels flat raided on Tuesday.
Abdeslam, a French national born in Brussels, had lived in Molenbeek before the 13 November attacks.
He has been the subject of a massive manhunt since the attacks, claimed by militants from the so-called Islamic State group.