He was shot to death after opening fire on a police van.
Paris prosecutor François Molins said shortly after the shootings that "the attacker's identity is known and has been verified".
A statement by IS's propaganda agency Amaq said the attacker was one of its "fighters", identifying him as "Abu Yussef the Belgian".
Two French officials said the gunman was detained towards the end of February after speaking threateningly about the police, but he was then released due to a lack of evidence.
Prime Minister Justin Trudeau posted a message on Twitter late Thursday saying "Canada stands with France, as we always will, against terror". Sunday's vote will be followed by a runoff on May 7 between the top two candidates.
Paris' iconic Champs-Elysees boulevard is reopen and picking up its usual early morning routine Friday. Police has also searched the home of the dead attacker in a town east of Paris.
Interior Ministry spokesman Pierre-Henry Brandet said on BFM television that a man came out of a auto and opened fire on a police vehicle.
The man who shot dead a French policeman in an Islamist militant attack had served time for armed assaults on law enforcement officers, police sources said on Friday, as authorities sought a second suspect flagged by Belgian security services.
"The man in the wanted notice issued by Belgian authorities presented himself to a police station in Antwerp", ministry spokesman Pierre-Henry Brandet told AFP.More news: Rangers even series with Canadiens
The gunman was shot dead at the scene and a pump-action shotgun and knives were found in his vehicle.
US President Donald Trump said: 'It looks like another terrorist attack.
The Frenchman was convicted of attempted murder after shooting at two police officers in 2001 when they tried to stop his stolen auto. The assailant reportedly targeted a police vehicle.
He said he and tourists fled to a shop.
France has been living under the state of emergency regime since the November 13, 2015 terrorist attacks in Paris and its northern suburb Saint-Denis, when a total of 130 people were killed and 350 injured.
"They were running, running", said 55-year-old Badi Ftaïti, who lives in the area.
French President Hollande quickly appeared on national television to share more details with a anxious nation.