PARIS (AFP) - French police found an abandoned car containing AK47 rifles on the outskirts of Paris, as the investigation into a series of attacks that killed at least 129 widened Sunday to five countries.
As the City of Light mourned its dead and world monuments were lit up in the red, white and blue of the French flag, authorities across Europe picked up suspects or launched probes.
French police discovered a black Seat car in the eastern suburb of Montreuil overnight that witnesses said was used by one of three groups of extremists responsible for the worst attacks in French history.
Seven of the gunmen wearing suicide belts died in the bloodshed - at the national Stade de France sports stadium and in or around the Bataclan concert hall in central Paris.
But prosecutors say they believe three groups were involved in the carnage claimed by the Islamic State in Iraq and Syria (ISIS) group.
Five people are in custody in Belgium and it is unclear if members of a third team are among the detainees or still on the run.
Police "took the two Kalashnikovs (out of the car), that we saw. They put them on the ground and emptied them," a witness who saw the seizure of the vehicle said on condition of anonymity. He said the Seat had Belgian plates.
Sources close to the investigation into the bloodshed confirmed that the car had been found.
The first of the seven dead attackers to be named was Omar Ismail Mostefai, a 29-year-old father and French citizen, identified from a severed finger among the carnage at the Bataclan concert hall, where 89 were killed in the worst of the bloodshed.
Police detained six people close to Mostefai, including his father, brother and sister-in-law, judicial sources said.
Born in the modest Paris suburb of Courcouronnes, he had eight convictions for petty crimes but had never served a prison sentence.
"It's a crazy thing, it's madness. Yesterday I was in Paris and I saw what a mess this was," one of his brothers saidbefore he was taken into custody on Saturday night.
In Belgium, police swooped on five suspects in Brussels and prosecutors said that two of the attackers were Frenchmen who had lived in the Belgian capital.
Meanwhile, German authorities were questioning a man from Montenegro found last week with a car-load of eight Kalashnikov rifles, three pistols and explosives.
The man, who was heading for Paris, has refused to cooperate with police.
The discovery of a Syrian passport near the body of one attacker has raised fears that some of the assailants might have entered Europe as part of the huge influx of people fleeing Syria's civil war.
Greek and Serbian authorities have confirmed the passport belonged to a man who registered as a refugee in October on the island of Leros and applied for asylum in Serbia a few days later.
But European Commission President Jean-Claude Juncker, who has urged EU countries to take in refugees, said there was no need for a complete review of the bloc's policies.
"Those who organised, who perpetrated the attacks are the very same people who the refugees are fleeing and not the opposite," he said.
Paris began three days of mourning as residents struggled to come to terms with the latest shock, 10 months after extremists hit satirical magazine Charlie Hebdo and a Jewish supermarket.
Traditional open-air markets were cancelled under stringent security procedures and many people stayed at home.
Outside the Bataclan venue where 89 people were killed in the worst of the violence, 38-year-old Herve came to pay his respects with his six-year-old son.
"We need to get out, you shouldn't stay at home," he said. "You need to go out and look, get a feel for yourself of what happened."
ISIS said itcarried out the attacks that left a trail of destruction at the sold-out Bataclan venue, restaurants and bars, and outside the Stade de France national stadium.
The group said they were acting in revenge for French air strikes in Syria and threatened further violence in France "as long as it continues its Crusader campaign".
President Francois Hollande has called the assault an "act of war" and vowed to hit back "without mercy".
Unlike those in January against Charlie Hebdo, none of the assailants had ever been jailed for terror offences.
Forensic teams were still scouring the Bataclan venue, where three attackers burst in shouting "Allahu akbar" (God is greatest) and sprayed gunfire during a gig by Californian band Eagles of Death Metal.
They are believed to have executed hostages one by one after rounding them up near the stage. Videos have shown terrified people scrambling out of a door and hanging out of windows to escape the violence.
As armed police stormed the venue, two gunmen blew themselves up, while the third was shot by police.
A former French intelligence chief, speaking on condition of anonymity to AFP, said it was likely the sophisticated suicide belts were manufactured in Europe and that the person who made them was likely still in Europe.
World leaders united Sunday to denounce terrorism at a heavily-guarded G20 summit in Turkey and observed a minute's silence in respect of those who were killed.
"We stand in solidarity with France in hunting down the perpetrators of this crime and bringing them to justice," US President Barack Obama said after talks with his host, Turkish President Recep Tayyip Erdogan.
Russia's Vladimir Putin said overcoming global terror was possible only "if all the international community unites its efforts".
London's Tower Bridge, Berlin's Brandenburg Gate and the World Trade Centre in New York were among the many landmarks lit up in the red, white and blue of the French national flag in a show of solidarity.