Paris suspect Salah Abdeslam has been wounded and arrested in a raid in Brussels, officials have said.
At least one suspect is believed to be holed up in a building 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.
But Belgian prosecutors told the BBC it was not clear exactly when he was at the flat because the prints could not be dated.
One man – identified as Algerian national Mohamed Belkaid and linked to the Paris attacks – was shot dead during the raid.
Officials said they believed as many as two other suspects may have escaped.
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 (IS) group.