Paris attacks suspect Salah Abdeslam has been wounded and captured in a huge anti-terror operation in Brussels after four months on the run.
Belgian Prime Minister Charles Michel confirmed the news at a press conference alongside French President Francois Hollande, hours after heavily armed officers stormed a building in the city's Molenbeek district.
Belgian police arrested five people in the raids including members of Abdeslam’s family who sheltered him, prosecutors said.
"A total of five people were arrested following three raids this afternoon," Thierry Werts, a spokesman for the federal prosecutor's office, told the press conference.
Mr Hollande congratulated the Belgian authorities and said moves would start to extradite Abdeslam, who was born in Brussels, back to France.
Mr Hollande said: "I have a special thought for the victims of the attacks on November 13 in Paris, because Salah Abdeslam is directly connected to the preparation, organisation and ... the perpetration of these attacks.
"I also think of the families who have been looking forward to these arrests, whether from close range or long distance, who are connected to that abomination."
Belgian migration minister Theo Francken confirmed the arrest of Abdeslam earlier tweeting: "We've got him."
The raids took place as EU leaders met on the other side of the city to discuss Europe's migration crisis.
Mr Michel left the summit early to attend to the situation in Molenbeek.
TV footage showed armed officers descending on the area and gunshots and explosions were reported.
Fire engines and ambulances were seen driving into a gated complex, which remains under armed police guard, and a helicopter hovered overhead.
Local media said police, who were joined at the scene by the army, appeared to use grenades while eyewitness reports suggested white smoke could be seen coming from a property.
At least ten gunshots were reportedly heard.
Belgian police had found fingerprints belonging to Abdeslam during an earlier operation, prosecutors said.
The Belgian federal prosecutor's office also said an Algerian killed during that earlier operation at the apartment in Brussels on Tuesday was probably one of the people French and Belgian investigators were seeking in relation to the attacks by the so-called Islamic State in Paris last November.
It later said in a separate statement that Mohamed Belkaid was probably the man who went under the name of Samir Bouzid and was killed on Tuesday.
Public broadcaster RTBF said it had information that Abdeslam, whose elder brother blew himself up in Paris, was "more than likely" one of two men who police have said evaded capture at the scene before a sniper shot dead 35-year-old Belkaid as he aimed a Kalashnikov.
Other Belgian media were more cautious, however, saying only there was evidence Abdeslam had been there.
A man named Samir Bouzid has been sought since December when police issued CCTV pictures of him wiring cash from Brussels two days after the Paris attacks to a woman who was then killed in a shootout with police in the Paris suburb of St Denis.
She was a cousin of Abdelhamid Abbaoud, a Belgian who had fought in Syria and is suspected of being a prime organiser of the attacks in which 130 people were killed.
Both died in the apartment in St Denis on 18 November.
France's BFM television said the fingerprints were found on a glass in the apartment, where four police officers, including a Frenchwoman, were wounded when a hail of automatic gunfire hit them through the front door as they arrived for what officials said they had expected to be a relatively routine search.
Belgian officials said earlier in the week that police had not expected to find armed suspects at the apartment and that the presence of French officers was not an indication the raid was of special importance to the investigation.
Abdeslam's elder brother was among the suicide bombers who killed themselves in Paris during a shooting rampage in which 130 people died.
The younger Abdeslam was driven back to Brussels from Paris hours later.
Belgian authorities are holding ten people suspected of involvement with him, but there has been no report of the fugitive himself being sighted.
There has long been speculation in Belgium that he could have fled to Syria.
Investigators believe much of the planning and preparation for the November bombing and shooting rampage in Paris was conducted in Brussels by young French and Belgian nationals, some of whom fought in Syria for Islamic State.
The attack strained relations between Brussels and Paris, with French officials suggesting Belgium was lax in monitoring the activities of hundreds of militants returned from Syria.
Brussels, headquarters of the European Union as well as Western military alliance NATO, was entirely locked down for days shortly after the Paris attacks for fear of a major incident there.
Brussels has maintained a high state of security alert since then, with military patrols a regular sight.