The Paris attacks suspect seized in a dramatic raid in Belgium on Friday is co-operating with Belgian police, his lawyer says.
Salah Abdeslam has been formally charged but is said to be resisting extradition to France.
The 26-year-old French national was arrested after four months on the run.
The Paris attacks last November left 130 people dead and dozens injured. So-called Islamic State (IS) said it was behind the bombings and shootings.
Investigators hope Salah Abdeslam, who was shot in the leg during his arrest, will reveal more information about the IS network behind the attacks, its financing and plans.
Officials allege he was in Paris on the night of the attacks but remain unclear what his exact role may have been. He is believed to have fled shortly afterwards, returning to the Molenbeek district of Brussels.
The European police agency, Europol, has meanwhile urged “extra vigilance” at borders following Friday’s Brussels raid.
Europol says more accomplices may try to flee Europe.
Senior security officials both in France and Belgium are meeting to assess the situation.
Salah Abdeslam’s brother, Brahim, was one of the attackers. He blew himself up.
The subject of a massive manhunt, Salah Abdeslam was arrested about 500m (1,600ft) from his home in Molenbeek.
Another man who was injured and arrested, Monir Ahmed Alaaj, was also on a wanted list, Belgian prosecutors said.
Three members of a family accused of harbouring Salah Abdeslam were also detained.
The raid came after his fingerprints were found in a flat in another Brussels district, which was raided on Tuesday.
Dramatic footage showed him being bundled into a police car after a volley of gunfire. Both suspects were discharged from hospital on Saturday.
French President Francois Hollande said Abdeslam’s arrest was “an important moment”.
“The battle against terrorism does not end tonight, even though this is a victory,” Mr Hollande told a news conference on Friday with Belgian Prime Minister Charles Michel.
“We must catch all those who allowed, organised or facilitated these attacks and we realise that they are a lot more numerous than we thought earlier and had identified,” he said.
Prosecutors said the second wanted man arrested in Molenbeek, Monir Ahmed Alaaj, had travelled with Abdeslam to Germany last October, where his fingerprints were taken during an identity check.
A false Syrian passport in Alaaj’s name and Belgian identity papers under an alias were found in a flat in the southern suburb of Forest that was raided on Tuesday.
Abdeslam’s fingerprints were also found in the Forest flat.
One man – identified as Algerian national Mohamed Belkaid and linked to the Paris attacks – was shot dead in Tuesday’s raid.
Officials have identified most of the people they believe to have carried out the assaults.
Most of the suspects either died during the attacks or were killed in subsequent police raids.