At 21:00 GMT on Thursday night a man pulled his auto alongside a bus transporting French police on the heavily-transited Champs-Elysees in Paris, opening fire with an automatic weapon and killing one of the officers.
French police are also hunting for a man who has been identified by Belgian security services, an interior ministry spokesman says. The prime minister said the government has reviewed its already extensive election security measures and says it is "fully mobilized" for Sunday's vote.
Authorities are investigating an attack by a gunman who opened fire on police on Paris' iconic Champs-Elysees boulevard Thursday night, killing one officer and wounding three people before police shot and killed him.
A note praising Islamic State (IS) was found near the body of the 39-year-old French attacker, who shot dead one officer and wounded two others before being killed by police.
France is in a state of emergency and at its highest possible level of alert since a string of Islamist militant attacks that began in 2015, which have killed over 230 people.More news: Washington Capitals beat Toronto Maple Leafs, tie series at 2 games apiece
Paris prosecutor François Molins said shortly after the shootings that "the attacker's identity is known and has been verified".
A property being searched in the eastern Paris suburb of Chelles is understood to be his home, according to a police document seen by the Associated Press news agency.
Security has been tight in the country, coming just days before the first round of France's presidential election on Sunday.
He was shot dead in return fire while trying to escape, police sources said.
Another witness identified only as Ines told French broadcaster BFM TV that she heard a shooting, saw a man's body on the ground and the area was quickly evacuated by police.More news: Paris Shooting: Why it could actually help Emmanuel Macron
Belgian officials had warned French authorities before the attack that El Osri was a "very risky individual en route to France" aboard a high-speed train.
NPR's Eleanor Beardsley reports from the Champs Elysees that the avenue has been completely cordoned off. "People are not allowed on it anymore".
France's interior ministry said the suspect had walked in to a police station in Antwerp, Belgium. Belgian authorities said they had no information about the suspect. "It's a awful thing that's going on in the world today".
Mr Macron, the front runner for the presidency, said candidates in the election should avoid one-upmanship following the attack and urged France not to "yield to fear, division and intimidation".More news: Atletico have edge in Champions League semis - Buffon
The attacks were claimed by Daesh, which is mainly active in Syria and Iraq.
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- One Officer Killed, Two Wounded In Shooting On Paris' Champs Elysees
- Paris attack: Police officer shot dead, another wounded, Champs Elysees closed off