A man gathers at a makeshift memorial at the Place de la Republique in Paris on Sunday, after a series of gun attacks occurred across the city.

Agencies/Paris

French police have identified one of the assailants in the co-ordinated attacks in Paris as Ismael Omar Mostefai, a 29-year- old French national, and seven of his relatives are being questioned, sources and French media said on Sunday.

Authorities had a dossier on Mostefai that marked him as a potential Islamist militant. He also had previous arrest records and had been sentenced eight times for petty crimes, according to French newspaper Le Monde.

Mostefai was one of the gunmen who blew himself up in a Paris concert hall where most of the 129 deaths from the attacks late on Friday took place.

His father, a brother and five other people are being held for questioning, several French media reported on Sunday, as the hunt continued for others involved in the shootings.

The reports said searches were also being conducted in the relatives' homes in the northeastern Aube region and in Essonne, south of Paris.

Father-of-one Mostefai was born in Courcouronnes, a southern suburb of Paris and lived in Chartres, southwest of the capital. He is suspected to have stayed in Syria between 2013 and 2014, Le Monde reported.

A source close to the investigation also confirmed media reports that a vehicle, a black Seat, used in the attacks was found with some arms onboard in Montreuil, a suburb in the east of Paris. Paris prosecutor Francois Molins said on Saturday that the Seat had been used in the attacks.

A Frenchman who thought to have hired another car used in the attacks was stopped at the Belgian border on Saturday morning, along with two other people, Molins said.

Molins said investigated believed three co-ordinated teams had carried out the wave of attacks across Paris. They were the worst in Europe since the Madrid train bombings of 2004, in which Islamists killed 191 people.

Friday's attacks were described as an "act of war" by President Francois Hollande.

The bloodshed came as France, a founder member of the US-led coalition waging air strikes against Islamic State in Iraq and Syria, was already on high alert for terrorist attacks. 

Paris quiet

The capital was strikingly quiet again on Sunday as residents struggled to come to terms with the latest shock, 10 months after jihadists hit satirical magazine Charlie Hebdo and a Jewish supermarket.

On the first of three days of national mourning, traditional open-air markets were cancelled under stringent security procedures and many people stayed at home.

IS jihadists have said they carried out the attacks that left a trail of destruction at the packed Bataclan venue, restaurants and bars, and outside the Stade de France national stadium.

The investigation stretches across Europe. Belgian police have arrested several suspects in Brussels, while German authorities are probing a possible link to a man recently found with a car full of explosive devices.

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 authorities have confirmed that the passport belonged to a man who registered as a refugee on the island of Leros in October and they are checking the fingerprints of a second man.

A total of 89 people were killed at the Bataclan concert hall by the armed men who burst in shouting "Allahu akbar" (God is greatest) before gunning down concert-goers watching Californian band Eagles of Death Metal.

They are believed to have executed hostages one by one. Video shows terrified people scrambling out of a door.

Suicide belts

As armed police stormed the venue, two of the gunmen blew themselves up, while the third was shot by police.

A former intelligence chief, speaking to AFP, said it was "very likely" the sophisticated suicide belts had been manufactured in Europe, perhaps even in France.

"The more you carry this stuff around, the more you multiply the risks. It is very likely that there is here, in France or in Europe, one or several guys who have come back from the lands of jihad where they learned the job," he said on condition of anonymity.

Three suicide bombers also detonated their explosives outside the Stade de France stadium where France were playing Germany in a football friendly attended by Hollande.

Several restaurants were targeted, including a popular Cambodian eatery in the trendy Canal St. Martin area, where at least 12 people died. Another 19 people were killed at a busy restaurant on nearby Rue de Charonne.

The seventh attacker blew himself up on a bustling avenue near the concert hall, injuring one other person.