Salah Abdeslam, the main suspect in the November Paris attacks, and several other suspects have been arrested in the Belgian capital.
Officials said the suspects were arrested in a police operation in Brussels' Molenbeek area on March 18.
Prosecutors said Abdeslam was slightly wounded after he was shot in the leg as police moved in on a flat.
"It's a very important result in the battle for democracy, for the values that we want to embody against this abominable form of obscurantism," Belgian Prime Minister Charles Michel said.
He was speaking in Brussels alongside French President Francois Hollande, who said he expected Abdeslam’s extradition "as quickly as possible."
Hollande also said the security threat level was “very high” and that "many more people" than originally thought were involved in the planning of the Paris attacks in which 130 people were killed.
Michel said a total of three suspects had been arrested. But a spokesman for the federal prosecutor's office, Thierry Werts, said that in addition to Abdeslam and another suspect linked to the Paris attacks, authorities were holding three members of a family that had sheltered Abdeslam.
Earlier, Belgian prosecutors said Abdeslam's fingerprints had been found in a Brussels apartment raided on March 15, but prosecutors said the prints could not be dated.
A man, identified as Algerian national Mohamed Belkaid and linked to the Paris attacks, was killed during the operation in the Forest suburb.
Abdeslam, 26, had lived in Molenbeek before the November 13 Paris attacks claimed by Islamic State militants.
A French national born in Brussels, he is suspected of having played a key logistical role in the assaults.
Abdeslam is believed to have returned to Belgium immediately after the attacks, in which his brother Brahim blew himself up.