A 29-year-old man has been killed and other four people wounded in a knife attack in the busy Opéra district of Paris on May 12.
According to witnesses, the suspect had shouted “Allahu Akbar” (God is greatest) before being shot dead by police.
ISIS later said one of its “soldiers” had carried out the attack.
France has been on high alert following a series of attacks in Paris and Lyon. More than 230 people have been killed by ISIS-inspired jihadists in the past three years.
Security forces have identified the attacker as being born in 1997 in the Russian republic of Chechnya, although he was not carrying any identification papers and has not been officially named. Chechnya is a republic in the North Caucasus region of southern Russia.
The republic declared independence in 1991 but Russian troops invaded in 1994 to quash it, sparking a decade-long conflict.
Jihadist groups, including those aligned with ISIS, have long operated in the region.
The judicial source told French media the suspect had no criminal record and that his parents had been held for questioning. Another source told Reuters the suspect was not previously known to police.
The suspect is believed to be a French national.
This is thought to be the first time an assailant of Chechen origin has carried out a terrorist attack in France.
France is home to some 30,000 people of Chechen origin.
France’s Interior Minister Gérard Collomb said the man who died was a 29-year-old passer-by, but gave no further details.
The four who were injured have also not yet been named. AFP news agency, citing sources, said a 34-year-old man and a 54-year-old woman were seriously hurt, while a 26-year-old woman and a 31-year-old man were slightly wounded.
Gérard Collomb said none had life-threatening injuries.
The attacker began stabbing passers-by at about 21:00 local time.
Eyewitnesses described him as a young man with brown hair and a beard, dressed in black tracksuit trousers.
The attacker tried to enter several bars and restaurants but was blocked by people inside.
Police first tried to stop the assailant with a stun-gun before shooting him dead, nine minutes after he began the attack.
A video tonight emerged of a man with b****ied hands, carrying knives and ranting “We swear by almighty Allah we will never stop fighting you”, after a serving soldier was ha**ed to death by two men just 200 yards from an Army barracks.
The man can be seen and heard talking to the camera. The video came as terrified eyewitnesses saw two men shot by police marksmen after the machete attack in Woolwich, south-east London.
The two men are thought to have waited around for 20 minutes until Metropolitan Police officers arrived and then tried to attack them – but were swiftly shot by armed policemen, including a woman.
They apparently shouted “Allahu Akbar” (God is great in Arabic), and tried to film the attack, the BBC’s political editor Nick Robinson said.
British Home Secretary Theresa May tonight called a meeting of the Government’s emergency Cobra committee in response to the machete and knife attack on the man who was wearing a Help for Heroes t-shirt.
Theresa May said she had been briefed on the killing by the head of MI5 and police later confirmed they were treating the incident as a possible terror attack.
Meanwhile PM David Cameron cancelled a meeting with French President Francois Hollande to return to London. He said Britain has faced similar terror attacks before and added: “We will never buckle in the face of it.”
Before the dramatic video of the b****ied man was obtained by ITV News, eyewitnesses said the “crazed” men in their 20s launched a ferocious attack and were “ha**ing, ch***ing and cu**ing him”.
In footage released by ITV News, a man with b****ied hands carrying a knife and a machete addresses people holding a camera, where he appears to attempt to justify the incident.
Speaking to those recording the scene he says: “I apologize that women had to witness this today, but in our land our women have to see the same.
“You people will never be safe. Remove your government, they don’t care about you.”
In footage obtained by The Sun, the man can also be heard saying: “You think David Cameron is going to get caught in the street when we start busting our guns you think politicians are going to die?
“No it’s going to be the average guy, like you, and your children. So get rid of them. Tell them to bring our troops back so you can all live in peace.”
Following his outburst, the man walks back towards where the victim is lying in the middle of the road. He then speaks to another man as they stand near to the victim.
Women are later seen bravely tending to the man lying. The footage appears to have been taken before any of the emergency services have arrived at the scene.
Later footage has also emerged from shortly after police fired at two men. One of the men can be seen lying in the road, while the second is laid on the pavement.
The footage taken after the shootings was reported to have been taken by a man who had been on a bus on his way to a job interview.
PM David Cameron said on Twitter that “the killing in Woolwich is truly shocking – I have asked the Home Secretary to chair a Cobra meeting”.
A Buckingham Palace spokesman said: “The Queen is of course concerned by the report of an attack in Woolwich earlier today. Her Majesty is being kept informed.”
The spokesman also confirmed the Queen will visit the King’s Troop Royal Horse Artillery at Woolwich barracks on May 31, which was planned before today’s attack.
This afternoon the area’s MP, Nick Raynsford, told BBC Radio 5 Live he believed the victim, a man aged in his 20s, was a serving soldier.
The man is believed to have been hacked to death after a car crash. The scene of the attack is just 200 yards from Woolwich Barracks.
Man who killed British soldier with a machete in Woolwich
Nick Raynsford said: “We think a serving soldier was the victim. We don’t know the circumstances surrounding the incident. We do know a number of weapons have been seized.
“They include a gun, various knives, and a machete, apparently. The police clearly had to take action in order to try and arrest these individuals.”
The Ministry of Defence said it was urgently looking at the reports that the incident involved a soldier but had no further comment.
Footage from a TV news helicopter showed a large number of weapons lying in the street following the incident. A London Ambulance Service spokesman said one man had died at the scene.
He added: “Our staff treated two others. Both men were taken to hospital, one of them is in a serious condition, the other is not.”
One witness, identified as James, said he and his partner saw two black men attack the young victim with knives, including a meat cleaver.
“They were hacking at this poor guy, literally,” he told LBC.
Metropolitan Police Commander Simon Letchford confirmed tonight that the two attackers were shot by armed officers.
He said in a statement: “At approximately 1420 we were called to reports of an assault in John Wilson Street, Woolwich, where one man was being assaulted by two other men.
“A number of weapons were reportedly being used in the attack and this included reports of a firearm.
“Officers including local Greenwich officers arrived at the scene and shortly after firearms officers arrived on the scene.
“On their arrival at the scene they found a man, who was later pronounced dead. At this early stage I am unable to provide any further information about the man who has died.
“Two men, who we believe from early reports to have been carrying weapons,were shot by police. They were taken to separate London hospitals. They are receiving treatment for their injuries.
“I can understand that this incident will cause community concerns and I would like to reiterate that we are investigating what has taken place today.”
Luke Huseyin, 32, who lives in a block of flats on John Wilson Street, Woolwich, close to where the incident happened said he watched two men murder a man before being shot.
He said: “I was at home and heard a big bang. I looked out of the window and saw a car had crashed.
“It was a blue Vauxhall. Then two black guys got out of the car dragging a white guy across the road towards the wall. One of the guys had a knife that looked about a foot long and a machete and the other bloke had a gun.
“They started slashing him up with the knife and hitting him in the stomach with the machete. I don’t think it took long before he was dead. There were people passing by who were screaming and running away. I’ve never seen anything like it.
“I’m still really shaken up. When he was dead, they dragged him out into the road and left him there. It was strange, they didn’t run off, they just stood there as if they were waiting for the police.
“It must have taken about 20 minutes for the police to arrive, I think it must’ve been because they were waiting for armed police.
“The police officers got out of the car and the two black men ran towards them with the gun.
“The police shot them. They fell to the ground. Then a helicopter landed. Think it must’ve been an air ambulance.
“The paramedics got out and I think they were working on the two men to try and keep them alive.
“I don’t know if they died, they were taken away in the helicopter. A blanket was put over the white guy lying in the road. I just can’t believe what I saw.”
Mother-of-four Julia Wilders, 51, said she was travelling past the scene and saw two men hacking at a man with meat cleavers.
“Graham was driving and we drove past the car which was up against a lamp post.
“There were two black guys that looked like they were trying to resuscitate a white guy on the floor. I thought there’d been an accident.
“But then I saw they were using meat cleavers to hack him up. We live just behind where it happened and once we got back we walked back to have a look and that’s when I saw one of the black guys pull out a handgun.
“My husband screamed at me to get back. I was petrified. As I was running back I saw the police pull up and the black guy was running towards the police car and they shot him.
“I didn’t see anything else, I just run back home.”
David Dixon is the headteacher of Mulgrave Primary School, which is located about 50 metres from the scene of the incident. He saw a body in the road after realizing something was happening and immediately locked down the school.
He said: “It was at the end of our road. As soon as we realized it was serious I went to see what had happened and then told staff to lock down the school and get the children inside. I spoke to police to ask what we should do.
“There seemed to be a body in the middle of the road. The traffic was backed up and the police were on the scene.”
Dzhokhar Tsarnaev, the 19-year-old Chechen terror suspect in Boston Marathon bombings, partied with college friends on Wednesday night and was said to “look relaxed” just two days after the horrific attack.
Hours before the deadly shootout which claimed his brother Tamerlan’s life Dzhokhar A. Tsarnaev was seen on a night out on campus.
A fellow University of Massachusetts student told the Boston Globe: “He was just relaxed.”
Dzhokhar Tsarnaev partied with college friends just two days after Boston Marathon terror attack
Dzhokhar Tsarnaev’s nonchalant attitude – a possible attempt to cover his tracks – in the wake of Monday’s Boston Marathon attack was also witnessed on his Twitter page.
At 5 p.m. on Monday – just hours after he and his older brother, Tamerlan Tsarnaev, were caught on surveillance footage coolly walking away from the bomb site – he tweeted: “Ain’t no love in the heart of the city, stay safe people.”
The next day Dzhokhar replied to a tweet claiming one of the fatalities in the bombings was a woman whose fiancé was proposing to her.
“Fake story” he wrote on the social media website.
The same day the suspect added: “I’m a stress free kind of guy.”