THE gunman who shot and killed a police officer on Paris’s Champs-Elysee, days before France’s presidential election, was detained in February for threatening police but later freed.

Anti-terrorism prosecutor Francois Molins said there was not enough evidence at the time to prove 39-year-old Frenchman Karim Cheurfi was a threat, though he did have a long police record – notably for trying to attack officers.

Investigators believe at this stage that Cheurfi acted alone when he killed Xavier Jugele and injured two other police officers and a German tourist in Paris on Thursday night. The injured officers were said to be out of mortal danger.

Molins said the attacker had a note defending extremists Daesh with him when he opened fire. The note, which apparently fell from his pocket, praised the group and listed the addresses of security sites.

Police shot and killed Cheurfi during the incident, and later found a pump-action shotgun and knives in his car.

Daesh has said it was behind the attack. In a statement from its Amaq news agency, it gave a pseudonym of Abu Yusuf al-Beljiki for the gunman, indicating he was Belgian or had lived in Belgium. But Belgium’s interior minister said the pseudonym did not belong to the attacker. Meanwhile, the French government was pulling out all the stops to protect tomorrow’s vote as the attack deepened France’s political divide.

“Nothing must hamper this democratic moment, essential for our country,” Prime Minister Bernard Cazeneuve said after a top-level meeting that reviewed the government’s already heightened security plans for the first of two rounds of voting.

“Barbarity and cowardice struck Paris last night,” he said as he appealed for national unity and for people “not to succumb to fear”.

One of the key questions is how the attack will affect the vote.

The two top finishers this weekend advance to a winner-takes-all run-off on May 7.

Two of the main candidates, conservative Francois Fillon and centrist Emmanuel Macron, cancelled planned campaign stops yesterday.

The attack brought back the recurrent campaign theme of France’s fight against Islamic extremism, one of the mainstays of the anti-immigration platform of far-right Front National leader Marine Le Pen and also, to a lesser extent, of Fillon, a former prime minister.

They redoubled appeals for a firmer hand against Islamic extremism and promised get-tough measures if elected.

Socialist Cazeneuve accused Le Pen in particular of seeking to make political capital from the attack.