A French policeman was shot dead and two others wounded in central Paris on Thursday night in an attack described as 'cowardly' by President Francois Hollande.
The assailant was also shot dead police as the incident struck the Camps Elysees boulevard - the heart of French tourism and history – that leads to the Arc de Triomphe.
Coming days before presidential elections, the shooting was quickly claimed by ISIS, with Hollande saying he was convinced it was an act of terrorism.
The area had been crowded with Parisians and tourists enjoying a spring evening moments before. Police were praised for preventing a bloodbath that could have ensued.
'The sense of duty of our policemen tonight averted a massacre ... they prevented a bloodbath on the Champs Elysees,' Interior Minister Matthias Fekl told reporters.
Paris Prosecutor Francois Molins said the man had been identified, but investigators were still assessing if he had accomplices.
A police arrest warrant issued earlier on Thursday, which was seen by Reuters after the attack, warned of a dangerous individual who had come into France by train from Belgium on Thursday. It was unclear if that man was the attacker or linked to the shooting.
Officers searched the home of the dead attacker in a town east of Paris, a police source said.
Explaining what happened, Interior Ministry spokesman Pierre-Henry Brandet, said: 'A little after 9 PM a vehicle stopped alongside a police car which was parked. Immediately a man got out and fired on the police vehicle, mortally wounding a police officer.'
France has lived under a state of emergency since 2015 and has suffered a spate of Islamist militant attacks mostly perpetrated by young men who grew up in France and Belgium and that have killed more than 230 people in the past two years.
Witness Chelloug, a kitchen assistant, told Reuters he was walking out of a shop and saw a man get out of a car and open fire with a rifle on a policeman.
'The policeman fell down. I heard six shots, I was afraid. I have a two year-old girl and I thought I was going to die... He shot straight at the police officer.'
ISIS, which is being driven out of its areas of territorial control in Iraq and Syria by Western-backed coalitions and has hundreds of French-speaking fighters, claimed responsibility for Thursday's shooting via its Amaq news agency, naming the attacker as Abu Yousif al-Belgiki.
The claim came quickly and the naming of the assailant suggested a degree of direct contact with Islamic State.
The group also claimed responsibility for a car attack in London last month killing four, but gave no name or details.
Police sources said the man was known to intelligence services. French television networks reported that he was a 39-year-old French national known for previous violent crimes.
The incident came as French voters prepared go to the polls on Sunday in the most tightly-contested presidential election in decades.
'We shall be of the utmost vigilance, especially in relation to the election,' said President Hollande, who is not himself running for re-election.
Additional reporting by Reuters.