The man at the centre of an intense manhunt in France and Belgium over the Paris attacks was stopped by police and let go, just hours after more than 100 people were killed.
A huge manhunt is under way for surviving members of the Islamist group that killed 132 people and injured about 350 - with 97 in a critical condition - in Paris on Friday night, and their accomplices.
Islamic State has claimed responsibility for the attacks.
The attackers opened fire and used explosive devices at seven locations across Paris, including a concert hall, restaurants, bars and outside a stadium.
French police have named Salah Abdeslam, 26, as a main suspect and issued an appeal for witnesses. They said he was dangerous and should not be approached.
Officers stopped a car carrying Mr Abdeslam towards the Belgian border but, according to French authorities, apparently let him and the other occupants of the car go after checking his ID.
Mr Abdeslam is one of three Belgium-based brothers linked to Friday's attacks, officials say.
Another, Brahim Abdeslam, 31, is said to have been an attacker who blew himself up outside a bar on the Boulevard Voltaire near the Bataclan, wounding one person.
A third brother, Mohammed, was reportedly arrested in the Brussels neighbourhood of Molenbeek while returning from Paris and remains in custody.
Belgian police said they had made a total of seven arrests in Brussels.
First attacker named
The first of seven dead attackers has been named as Ismail Mostefai. Six people close to him are in custody.
Two other attackers were French nationals living in Belgium, prosecutors said.
Mostefai was reportedly identified after investigators found a severed finger at the scene of the worst atrocity, the Bataclan concert hall.
He came from the town of Courcouronnes, south of Paris, and had lived in the city of Chartres 100km south-west of Paris until 2012 and had regularly attended a mosque there.
French judicial sources said several Kalashnikovs had been found in an abandoned car believed to have been used by some of the Paris attackers.
The black Seat car was found in the eastern Paris suburb of Montreuil on Sunday, suggesting some of the attackers got away.
The car was believed to have been used by gunmen who opened fire on people in restaurants on Friday, police said.
Several AK47 rifles were found in the car, French media quoted judicial sources as saying.
The Seat and another car used in the attacks - a Volkswagen Polo - were rented in Belgium.
The black VW was found near the Bataclan concert venue, where nearly 90 people were killed.
It is widely believed now that at least one of the attackers, Abdeslam, managed to get away from the scene.
Paris chief prosecutor Francois Molins said on Saturday there were probably three co-ordinated teams of terrorists behind this barbaric act.
"We have to find out where they came from... and how they were funded."
Belgian 'jihadists' haven'
French Interior Minister Bernard Cazeneuve said Friday night's attacks in Paris had been prepared "by a group of individuals based in Belgium" who had "benefited from accomplices in France".
One of the Paris attackers lived in Brussels and another in the nearby town of Molenbeek, Belgian prosecutors had said on Sunday, without naming either.
Belgium's Premier Charles Michel said the Belgian authorities would crack down on Molenbeek, which had a reputation as being a haven for jihadists.
"I have noticed there is almost always a link to Molenbeek, that there is a gigantic problem there," he said.
Brussels mayor Yvan Mayeur added: "We must stop being a base for those who make war in Europe."
French media reports have named Bilal Hadfi, who also lived in Belgium, as one of three men who blew themselves up outside the Stade de France on Friday.
Notre Dame service
A memorial service for the victims of the weekend's terror attacks on Paris was held at Notre Dame cathedral this morning.
At the same time, thousands of people gathered around shrines to the victims in a show of solidarity.
A false alarm sent those in the streets scattering when they thought they heard gunshots, showing how much on edge people remain in the city, 48 hours after the attacks.
Paris archbishop Cardinal Andre Vingt-Trois said the French capital had been hit with particular savagery.
Prime Minister Manuel Valls said most of the bodies had been identified and that the process should be completed in the coming hours.
A Syrian passport, found near the body of one of the attackers at the Stade de France, had been used to travel through the Greek island of Leros last month, Greek officials have confirmed.
Serbia says the holder of that passport had also crossed its border from Macedonia and sought asylum at one of its registration centres.
No direct link has yet been made with the holder of the passport and the attackers.
Centralised attack, says expert
Meanwhile, an expert on Islamic State said the level of sophistication of the Paris attacks suggested it was centrally organized.
Will McCants - the director of the Brookings Institution's Project on US Relations with the Islamic World - told Nine To Noon it was still not known if Islamic State central in Syria and Iraq organised the attacks, but there were indications of chatter between the attackers and the defacto headquarters of the Islamic State before the attack.
It may be one of a series of attacks over the last few weeks co-ordinated by Islamic State central, he said.
"And if that's the case, it's very worrisome because they're not just an insurgent group, they control a lot of territory and control a lot of financial resources that they can dedicate to foreign operations."
The Paris attacks would mean it was much more difficult for Syrian refugees to enter countries of the European Union, and border controls will be tightened, Mr McCants said.
- BBC / Reuters / RNZ