Europe's most wanted man was captured after a shootout in Brussels in a major coup for authorities investigating November's Islamic State attacks on Paris.
Salah Abdeslam, 26, the first suspected active participant taken alive, was being held overnight in hospital with a slight leg wound, Belgian Prime Minister Charles Michel announced at a news conference alongside French President Francois Hollande.
"This is an important result in the battle for democracy," Michel said on Friday, adding that U.S. President Barack Obama had called to congratulate the Belgian and French leaders.
A Belgian minister broke the news by tweeting, "We got him."
Prosecutors said a second wanted man, who used the false name of Amine Choukri, was also wounded and captured in the raid on the apartment in Abdeslam's home neighborhood of Molenbeek.
The operation, planned after fingerprints and passports were found in a bloody raid three days earlier, was staged in a rush after media leaked word that police had found Abdeslam's trail.
Hollande, who was visiting Brussels for a European summit, confirmed France would seek extradition for the Brussels-based Frenchman who, he said, was definitely in Paris on the bloody night of Friday, Nov. 13 when 130 people were killed.
Abdeslam's elder brother, a Brussels barkeeper who shared a chequered history of drugs and petty crime, blew himself up outside a Parisian cafe that night. Hollande said the younger man's role in the killings was unclear but investigators were sure he helped plan the operation for the Syria-based group.
Since all the identified attackers were killed, Abdeslam offers France a major new chance to understand what happened.
It was now clear, Hollande said, that many more people had been involved in the Paris attacks on a sports stadium, bars and cafes and concert hall than was first thought. Security concerns remain, he added, "The threat level is very high."
Television footage showed armed security forces dragging a man with his head covered out of a building and into a car.
Several bursts of gunfire rang out earlier in Molenbeek, a down-at-heel borough that is home to many Muslim immigrants, notably of Moroccan descent like Abdeslam's family. Two explosions were heard after the arrest, though it was unclear whether they were part of a new operation or the clear-up.
Some four hours later, the main police presence had stood down but crime scene investigators were still at work.
There had long been speculation about whether Abdeslam had stayed in Belgium or managed to flee to Syria.
Security services will be seeking information from Abdeslam on Islamic State plans and structures, his contacts in Europe and Syria and support networks and finance. Over the past four months, France and Belgium have detained several people linked to the prime suspects but none they suspect of a major role.