French prosecutors have opened a terrorism investigation into the Champs-Elysees attack on Paris police officers.
One officer has been confirmed dead in the incident which occurred in the French capital earlier tonight.
There had been reports that a second policeman had died after the shooting but that is not now believed to be the case.
Police sources say the person who fired on them has also been killed and authorities are warning people to avoid the Champs-Elysees area.
French President Francois Hollande has scheduled an emergency meeting following the shootings.
Paris police spokeswoman Johanna Primevert said that the attacker targeted police guarding the area near the Franklin Roosevelt subway station on Thursday night at the centre of the avenue popular with tourists.
The attack came three days before the first round of France's tense presidential election.
Security is high around the vote after France has been attacked in recent years.
Police had arrested two men on Tuesday in what they described as a thwarted terror attack.
The incident recalled two recent attacks on soldiers providing security at prominent locations around Paris, one at the Louvre museum in February and one at Orly airport last month.
A witness identified only as Ines told French television station BFM that she heard a shooting and saw a man's body on the ground before police quickly evacuated the area, where she works in a shop.
A French television station hosting a televised event with the 11 candidates running for president briefly interrupted its broadcast to report the shootings.
None of the candidates immediately commented.
The French Interior Ministry said the attack deliberately targeted police officers guarding the area.
Spokesman Pierre-Henry Brandet said on BFM television that a man came out of a car and opened fire on a police vehicle.
Mr Brandet said the police officers were "deliberately" targeted.
He said police were securing the area but there is "no other police operation under way" there.
He said it was too early to say whether the attacker might have had an accomplice, and said authorities were studying multiple potential motives.
US President Donald Trump, speaking in Washington during a news conference with Italian Prime Minister Paolo Gentiloni, said the shooting "looks like another terrorist attack" and sent his condolences to France.
Police and soldiers sealed off the area, ordering tourists back into their hotels and blocking people from approaching the scene.
Emergency vehicles blocked the wide avenue that cuts across central Paris between the Arc de Triomphe and the Tuileries Garden, normally packed with cars and tourists.
