Champs Elysee gunman was arrested in February - police swoop on Paris home of Karim Cheurfi
- Gunman was arrested earlier this year
- Islamic State claim responsibility
- Attack threatens to have bearing on voters' decisions
- Police officer shot dead, two seriously wounded
The gunman who shot and killed a police officer on the Champs-Elysees in Paris was detained in February for threatening police and then freed.
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.
An address searched in the town of Chelles has been identifued as belonging to the family home of 39-year-old Karim Cheurfi, who has a criminal record. Police tape surrounded the quiet, middle-class area and neighbours expressed surprise at the searches.
Archive reports by French newspaper Le Parisien say Cheurfi was convicted of attacking a police officer in 2001.
Authorities are trying to determine whether "one or more people" might have helped the attacker, Interior Ministry spokesman Pierre-Henry Brandet said at the scene of the shooting.
Police shot and killed the gunman after he opened fire on a police van on Paris' most famous boulevard on Thursday night.
The Islamic State group quickly claimed responsibility for the attack.
The Paris prosecutor's office leading the investigation has said a pump-action shotgun and knives were found in the gunman's car. Police have detained for questioning three of his family members, as investigators seek to determine whether he was acting alone and where he got his weapons. A Belgian man who had been linked by some as an accomplice to the gunman has turned himself in, and authorities said there was no link to the incident.
The Islamic State extremist group quickly claimed responsibility for Thursday night's attack, just three days before a tense presidential election. Security has already has been a dominant theme in the campaign and the violence on the city's iconic avenue threatened to have a bearing on voters' decisions.
Candidates cancelled or rescheduled final campaign events ahead of Sunday's first-round vote. Investigators searched a home early on Friday in an eastern suburb of Paris believed to be linked to the shooting.
US vice president Mike Pence said the shooting was the "latest reminder that terrorism can strike anywhere, any time" and his country "will not relent in our effort to end terrorism".
One police officer was killed and two colleagues seriously wounded when the attacker emerged from a car and used an automatic weapon to shoot at officers outside a Marks & Spencer store at the centre of the Champs-Elysees, anti-terrorism prosecutor Francois Molins said.
The gunman was shot dead by other officers. A female foreign tourist also was wounded, Mr Molins said.
Australia's prime minister offered his country's prayers for the shot police officers and urged Australians in Europe to be on their guard.
Malcolm Turnbull urged travellers to check for security warnings on the Australian Department of Foreign Affairs and Trade website.
"Everywhere - but especially in Europe at the moment - pay close attention to your surroundings," he told Australia's Seven Network.
Mr Turnbull says regional security would be among the topics he would be discussing with US vice president Mike Pence in Sydney on Friday.
The IS group's claim of responsibility just a few hours after the attack came unusually swiftly for the extremist group, which has been losing territory in Iraq and Syria.
In a statement from its Amaq news agency, the group gave a pseudonym for the gunman, Abu Yusuf al-Beljiki, indicating he was Belgian or had lived in Belgium.
President Francois Hollande said he was convinced the circumstances of the attack in a country pointed to a terrorist act.
Mr Hollande held an emergency meeting with the prime minister on Thursday night and will convene a meeting of the defence council on Friday morning.
The incident recalled two recent attacks on soldiers providing security at prominent locations around Paris: one at the Louvre museum in February and one at Orly airport last month.
Speaking in Washington during a news conference with Italian prime minister Paolo Gentiloni, US president Donald Trump said the shooting "looks like another terrorist attack" and sent condolences to France.
A witness identified only as Ines told French television station BFM that she heard a shooting, saw a man's body on the ground
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