- Video report by ITV News Correspondent Richard Pallot
A police officer has been killed, and two officers and a female tourist injured in a shooting in the centre of Paris.
Here is what we know about the attack so far.
- What happened?
A gunman opened fire on police officers outside a Marks & Spencer store on the Champs-Élysées in central Paris.
One policeman has been confirmed killed, and two others were wounded. A female foreign tourist was also injured.
The attacker, who was wielding a Kalashnikov gun, was shot dead at the scene.
The French interior ministry said the attack deliberately targeted police officers guarding the area.
- Who was the gunman?
The attacker was named by French prosecutors as Karim Cheurfi, a French national with a long history of violence and criminal offences.
Prosecutors confirmed he had carried a note defending the so-called Islamic State which was found near his body.
Cheurfi had spent long stretches in prison and was recently arrested, apparently for threatening policemen, but was released due to lack of evidence.
Officials said he had never been flagged as a potential extremist.
A second man later flagged by Belgian security services in connection with the shooting attack has handed himself in to police in Antwerp, the Belga news agency reported.
Three family members of the slain gunman have also been detained, a French legal source said.
- Who were the victims?
The slain officer has been named as Xavier Jugele, 37, in a statement from the LGBT policing organisation Flag!
It emerged that the officer had previously responded to the terror attack at the Bataclan in Paris in November 2015.
Mr Jugele attended the re-opening of the Bataclan a year later, saying he was there to "defend our civic values" and "say no to terrorists".
The other officers and the tourist injured in the attack have not yet been named.
- Is the attack terror-related?
Early details suggest that the attack may have been terror-related, though officials have been keen to stress that it is too early to confirm that and they are still working to establish a motive.
A written note defending the so-called Islamic State was found next to the body of the gunman.
French President Francois Hollande has said he is convinced the shooting was terror-related.
The so-called Islamic State has also said it was behind the attack.
However, that claim has not been independently verified and the terror group also named the attacker under a pseudonym which incorrectly said he was a Belgian, throwing doubt on the truth of their statement.
- What has been the reaction in Paris?
The centre of Paris was largely shut down and several metro stations closed amid a major operation around the Champs-Élysées.
Tourists were sent fleeing by the sound of shots in the major hot spot for visitors to the French capital.
French President Francois Hollande was due to host an emergency meeting over the shooting.
There is also speculation over whether the attack could affect the presidential elections, with polls due to open within days.
Some candidates in the French presidential election have cancelled campaign events following the shooting.
- What has the UK said?
Downing Street has condemned the attack and Prime Minister Theresa May has expressed her condolences to President Hollande, a Downing Street spokesman said.
The UK foreign office said British citizens in Paris should "remain vigilant and follow the advice of the local security authorities and/or your tour operator".
Steve White, chairman of the Police Federation of England and Wales, said: "Once again the police family is in mourning and it serves to underline how brave officers are putting their life on the line day in and day out to protect the public."
Making reference to last month's Westminster attack in which police officer Keith Palmer was killed, he added: "As French colleagues felt the pain of our loss in Westminster last month, we feel theirs tonight."