A known terror suspect shot dead a French policeman and wounded two others on Paris's Champs Elysees in an attack claimed by the self-styled Islamic State terrorist group days before a presidential election.
The attack also shows the ongoing threat in France and elsewhere in Europe and it could lead to growing public pressure on governments to stop Islamic terrorism.
He was shot dead in return fire while trying to escape, police sources said.
After Islamic State claimed responsibility for the Champs Elysée shooting, and identified the attacker as "Abu Yousif the Belgian", some media outlets reported a Belgian connection involving a supposedly unsafe individual called Osri who was en route to France on the Thalys.
The officials said the gunman was detained toward the end of February after speaking threateningly about the police, but then released for lack of evidence.
He had been convicted in 2005 of three counts of attempted murder, two involving police officers, sources said.More news: Facebook's latest internet-beaming drone is a tiny tethered helicopter
Three people associated with Cheurfi have been detained for questioning, though his connection to those individuals was not publicly released.
He was found to have an alibi because he was at his place of work, the spokesman said.
Police shot and killed Cheurfi after he opened fire on a police van on Paris' most famous boulevard.
French President Francois Hollande classified the incident as a terrorist attack.
France has been under a state of emergency for almost a year and a half, with more than 230 people killed in terror attacks since the start of 2015.
Hollande is meeting with his top defense and security leaders on Friday.
United States president Donald Trump was among the first leaders to express his sorrow over the shootings in Paris.More news: Why organ donation is so important
Several candidates in Sunday's presidential election announced after the attack that they ended their campaigns early as a mark of respect.
Republican Francois Fillon, the National Front's Marine Le Pen, centrist Emmanuel Macron, and Socialist Benoit Hamon all cancelled events planned for Friday and instead made televised statements about how they'd fight terrorism.
The terrorist group said it was behind the attack and named the gunman as Abu Yusuf al Beljiki, suggesting he was from Belgium.
Two police officers were injured in the assault, one of whom remains in hospital.
A French television station hosting an event with the 11 candidates running for president briefly interrupted its broadcast to report the shootings.
Soldiers were patrolling the area and the cordon was extended to the streets surrounding Champs Elysees.More news: Trade in the Foreground of Pence Tour
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