Police have taken into custody the father and brother of one of the attackers involved in a series of coordinated terrorist strikes in Paris that claimed the lives of at least 129 people.

The 29-year-old French national from a Paris suburb, who died in the attacks, had been identified as “radicalised” by police.

The man was identified by French newspaper Le Monde as Ismael Omar Mostefai.

• Parisians sing anthem in the face of violence
• Paris attacks: what we know so far
• Paris under siege: the tragedy in pictures

He was identified using a severed fingertip.

Born on November 21 1985, in the poor Paris suburb of Courcouronnes, Mostefai’s criminal record shows eight convictions for petty crimes between 2004 and 2010, but no jail time.

His brother, who is 34, contacted police on his own initiative before being taken into custody along with his father.

“It’s a crazy thing, it’s madness,” his brother told AFP, his voice trembling, before he has taken into custody.

“Yesterday I was in Paris and I saw how this shit went down.”

Police searched the family’s home in the small town of Romilly-sur-Seine, 130 kilometres east of Paris, as well as his brother’s in nearby Bondoufle.

French prosecutor Francois Molins said there were seven attackers killed in total, working as part of three “teams” to carry out the terrorist acts, in which gunmen and bombers targeted the Bataclan concert hall, a series of bars and restaurants and the Stade de France sports venue.

The mood around Paris in this first 24 hours after the horror seemed sombre.

Under a grey sky, people clustered close to police blockades, laying flowers, walking the few blocks from one horror site to another.

They stared at the front of the Casa Nostra restaurant, where bullet holes marked the glass and sand covered the blood. At least five people died here.

The Bataclan club, where the majority of victims were killed, was blocked from clear view by police and trees.

It is almost 11 months since the Charlie Hebdo murders and Parisians are now facing an even greater horror.

That terror attack against a satirical newspaper was shocking enough.

Many of them told the ABC this shows there is no limit to how far their enemies will go.

These massacres have made them feel so much more vulnerable.

The attacks left more than 350 people injured, including 99 who were in a serious condition.

The prosecutor said all of the attackers used Kalashnikov assault rifles and wore the same type of suicide vests with shrapnel mixed with explosives, intended to cause maximum casualties.

A Syrian passport was found near the body of one of the terrorists who detonated a bomb outside gate D of the Stade de France, killing himself and a passerby.

Greek officials confirmed the passport had been used by its owner to pass through the island of Leros near the coast of Turkey on October 3.

However, it was not known whether the document was checked in other countries on the way to France.

Another man being traced in connection with the attacks by French police had also registered in Greece, police sources said, with local media reporting he had arrived on Leros in August.

Little was known about the others involved, however, it is believed three teens were involved.

Belgian police arrested three suspects on Saturday, including one who was in the French capital at the time of the carnage, Belgian prime minister Charles Michel said.

Mr Michel told Belgian television the arrests were linked to “suspect vehicles” identified during the investigation by French police.

He told RTBF television it was “believed or suspected that one of these people was in Paris last night”.

The Paris prosecutor said that one of the vehicles — a grey Volkswagen Polo — used in the attacks was registered in Belgium and hired by a French national living in Belgium.

The car was found near the Bataclan concert hall in the French capital where scores of people were killed, Belgium’s justice minister said.

Parking tickets from Molenbeek in Brussels were found inside the car, according to Belgian media.

European security officials have previously voiced concerns jihadists could take advantage of the flow of asylum seekers that Europe has experienced this year.

“It is clear now that together with the victims of Islamo-fascism in the Middle East that come as refugees, extreme elements are crossing to Europe,” Greek defence minister Panos Kammenos said.

However, prime minister Alexis Tsipras insisted the refugees fleeing Syria “are hunted by the same terrorists” that struck Paris.

“We must find solutions to the drama of the people who leave their homes, hunted by the same terrorists, and drown in the Mediterranean,” he said in a televised address.

Attacks strengthen need for Syrian solution: Turnbull

Australian Prime Minister Malcolm Turnbull said the attacks strengthened the need to find a political solution to the Syrian crisis and said the terrorists acting in the name of God were “utterly godless”.

“These terrorists commit a double crime. They are murderers. They are mass murderers,” he said.

“They are barbarians, but at the same time, they also defame religion. They defame, they blaspheme, they defame Islam.”

He said he had discussed the screening of Syrian refugees since the Paris attacks.

“While there have been some exceptions, the history of terrorist activities in Australia and people of concern in this area is very much for the most part second and third-generation Australians,” he said.

Addressing French president Francois Hollande’s claim the terrorist attacks were an were an “act of war”, Mr Turnbull said: “It’s guns and bombs, yes, it does look like a war.”

“But … we have to recognise that the resources, the strength of our states, of our nations, are so much greater than those of the terrorists.”

Mr Turnbull said terrorism would be a major issue at G20 talks in Turkey.

‘Act of war’

French President Francois Hollande says the terror attacks on Paris were an “an act of war” and blamed Islamic State for the bloodshed.

In televised address on Saturday (local time), Mr Hollande said the violence, which claimed 129 lives, was committed by “the Islamic State group … against France, against the values that we defend everywhere in the world, against what we are: a free country that means something to the whole planet”.

The group claimed responsibility for the attacks in a statement released in both French and Arabic.

“Eight brothers, wrapped in explosive belts and armed with machine rifles, targeted sites that were accurately chosen in the heart of the capital of France,” it said.

“Let France and those who walk in its path know that they will remain on the top of the list of targets of the Islamic State.”

Mr Hollande issued a warning to the perpetrators, saying France “will be merciless toward the barbarians of Islamic State”.

It was Mr Hollande’s second address following the attacks. Late on Friday he said authorities know where the attack came from, “who these criminals are, who the terrorists are”.

“We are going to lead a war which will be pitiless,” he said.

He declared three days of mourning for the nation and put the country’s security on the highest alert level.

The aftermath

The statements came as Paris and the world began to comprehend the scale of the tragedy. It was the deadliest terrorist attack on European soil since the 2004 train bombings in Madrid and the worst violence to strike France since World War II.

The attacks led to chaotic scenes on the streets of Paris, with the dead and wounded lying amid shattered glass and upturned tables on the roadside. Weeping relatives tended to the wounded.

Witness Pierre Montfort lives close to a Cambodian restaurant on Rue Bichat, where one of seven attacks took place in a night of bloodshed not seen in decades.

“We heard the sound of guns, 30-second bursts. It was endless. We thought it was fireworks,” he said on Friday night.

Another witness described the scene: “For a moment, we could only see the flames from the gun. We were scared, how did we know he wasn’t going to shoot the windows?”

Bataclan bloodbath

A rock concert at the Bataclan concert hall was the scene of the highest death toll, with early reports suggesting more than 100 people had been killed. The number was later revised down to 87.

Eyewitnesses said a number of gunmen with AK47-style weapons entered the theatre during a concert by a US rock band and held up to 1500 patrons hostage. When police moved to end the siege, the terrorists opened fire on the crowd, killing scores.

Three of the attackers blew up suicide vests as police launched their attack, several sources said. The fourth was hit by police fire and blew up as he fell.

“There was blood everywhere, corpses everywhere. We heard screaming. Everyone was trying to flee,” said Pierre Janaszak, a radio presenter who attended the concert and hid with several others at the venue.

Emma Grace Parkinson

Australian victim

Foreign minister Julie Bishop said at least one Australian was among the injured, 19-year-old Emma Parkinson from Hobart.

“(We are) aware of an Australian who has been injured in the Paris attacks and we are providing consular assistance,” Ms Bishop said.

Ms Parkinson’s family said she was shot at the Bataclan theatre where she was attending a concert by American band Eagles of Death Metal and her condition is unknown.

Soon after the tragedy, Mr Hollande declared a state of emergency across the entire country, closing the national borders and imposing curfews — the nation’s first since the 1940s.

Paris remained in a state of emergency as the city awoke on Saturday, with public amenities like museums, libraries, gyms pools and markets ordered to close.

All the city’s weekend sporting fixtures have been cancelled.

Paris attacks at a glance

Attack sites: 6
Attackers: 8
Attackers killed by suicide bombs: 7
Attacker shot dead: 1
Explosions heard at Stade de France: 2
Total Death Toll: 129
Injured: more than 352, 99 in a critical condition
Soldiers deployed around the city: 1500
Capacity of Bataclan Hall: 1200

Police stand guard outside a restaurant, a body shrouded beside them. Photo: Getty

Are you searching for family or friends?

The Foreign Minister has urged those concerned about Australians in France to contact the emergency consular line.

Within Australia: 1300 555 135
Outside Australia: +61 2 6261 3305

-with Darren Devlyn, Jackson Stiles, Anthony Colangelo, Susannah Guthrie and agencies