The 11 candidates were appearing on a television programme ahead of the first round of voting in the two-part election on Thursday night when the attack on the Champs Elysees boulevard that left one officer dead happened.
French interior ministry spokesman Pierre-Henry Brandet told reporters the shooting started when a auto stopped alongside a stationary police vehicle. Another officer and a bystander were injured. Also wounded was a female tourist.
Paris police spokeswoman Johanna Primevert told The Associated Press that the attacker targeted officers guarding the area near the Franklin Roosevelt subway station at the center of the avenue popular with tourists.
Speaking after the attack, French President Francois Hollande said security forces would be vigilant during the forthcoming presidential election.
In this image made from video, police attend the scene after an incident on the Champs-Elysees in Paris, Thursday April 20, 2017.
ABC News says the suspect has been killed.
Investigators searched a home early Friday in an eastern suburb of Paris believed linked to the attack.
Two police sources said the gunman had been flagged as an extremist.
"The perpetrator of the attack in Champs Elysee in central Paris is Abu Yussef the Belgian and he is one of the Islamic State's fighters", IS claimed in a statement by the jihadists' propaganda agency Amaq.
Authorities are trying to determine whether "one or more people" might have helped the attacker, Interior Ministry spokesman Pierre-Henry Brandet told reporters at the scene of the shooting.
Paris Prosecutor Francois Molins said he will reveal the shooter's identity on Friday at a news conference.
A second suspect thought to be involved in the incident on the Champs Elysees shopping boulevard just days ahead of France's presidential election was still on the loose.
The attacker, who was in a vehicle, opened fire on a police auto at a red light, killing an officer inside.
The attacker was being investigated over his possible intention to kill police officers, sources close to the investigation said.
As the first details filtered through about the attack, US President Donald Trump sent his condolences and said that "it looks like another terrorist attack".
The attack occurred on the most famous avenue in Paris, not far from another landmark, the Arc de Triomphe.
France has lived under a state of emergency since 2015 and has suffered a spate of Islamist militant attacks that have killed more than 230 people in the past two years.
Conservative French presidential hopeful Francois Fillon tweeted, "Paying homage to police who give their lives to protect ours, #ChampsElysees".