A police officer has been killed and two others injured in a suspected terrorist shooting in the centre of Paris.
The attacker opened fire on a police car parked on the Champs-Elysees before he was also shot dead, the French Interior Ministry said.
Police have not given a possible motive for the attack but a terrorism investigation has been launched.
French officials said the suspect in the attack was previously flagged as an extremist.
The world-famous avenue has been sealed off and nearby stations on the Paris Metro have been closed.
French police warned the public to stay away from the area and armed officers are at the scene.
They also asked people not to “spread any misinformation” that has not come from a “trusted source”.
The incident comes days before the French election, which is to take place on Sunday.
President Francois Hollande has called an emergency meeting on Thursday evening.
Tourists have been warned to go back to their hotels and to let family and friends know that they are safe.
The UK Foreign Office said: “The British Embassy is in contact with local authorities and urgently seeking further information following reports of a shooting incident on the Champs-Elysees in Paris.
“You should remain vigilant and follow the advice of the local security authorities and/or your tour operator.
“If you’re in the area and it is safe to do so, contact your friends and family to tell them you are safe.”
France’s Prime Minister Bernard Cazeneuve paid tribute to the officer and tweeted that his thoughts are with the family.
US President Donald Trump, speaking at a press conference in Washington, said the incident “looks like another terrorist attack” and sent his condolences to France.
Steve White, chairman of the Police Federation of England and Wales, tweeted: “The policing family is in mourning yet again.”
Mr Hollande said at a press conference that he is convinced the attack was a terrorist act.
Mr Hollande tweeted that his thoughts went to the family of the dead policeman and relatives of the wounded.
Steve White, chairman of the Police Federation of England and Wales, said “thoughts and sympathies go out to the families and colleagues of all those affected”.
“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,” he said.
“As French colleagues felt the pain of our loss in Westminster last month, we feel theirs tonight.”
The Islamic State extremist group has claimed responsibility for the attack.