Terror suspect Karim Cheurfi is pictured

French security services are today facing troubling questions as to how they failed to prevent an ISIS gunman slaughtering one policeman and wounding two other officers when he was already on a terror watch list.

The Champs-Elysees killer - identified as Karim Cheurfi - had been detained only last month, it has emerged, after informants said he was 'seeking to obtain weapons to kill policemen'.

But the 39-year-old, who used the war name 'Abu Yousuf the Belgian', had to be released because anti-terror police did not have enough evidence to hold him.

The homegrown fanatic, who officials confirmed was a French national despite his nickname, had also been released early from prison – where it is thought he was radicalised – having been jailed for 20 years in 2005 for trying to kill two policemen.

Cheurfi opened fire five times with a .38 revolver following a car chase in 2001, leaving the officers and a third victim wounded.

He had fled on foot before the driver of the other car and the passenger - a trainee police officer - caught up with him. He fired twice, seriously wounding both men in the chest. All three survived the attack in Roissy-en-Brie, in the Seine-et-Marne department of northern France.

Cheurfi was arrested and placed in custody under a false name. Two days later he seriously injured an officer who was taking him out of his cell, seizing his weapon and firing several times.

Two French officials said this morning that Cheurfi was detained in February for threatening police before being freed, although a warrant for his arrest is dated March 6.

Over the past few months he had reportedly been undergoing psychiatric and terrorist investigations for uttering death threats against law enforcement officials.

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The killer was known to security services in France, according to reports emerging last night

One police officer was shot dead and two more seriously injured by a gunman carrying a Kalashnikov in Paris

Pierre-Henry Brandet, spokesman for France's Interior Ministry, confirmed that one police officer was dead and two seriously wounded following the 'targeted attack'

The arrest warrant issued for Cheurfi before he was detained at the beginning of last month

The ISIS killer is believed to have been released in 2016 following the triple assassination attempt, at a time when he was known for drug offences, car theft and robbery.

Despite having the nickname 'Abu Yousuf the Belgian', Cheurfi was a French national, Belgian interior minister Jan Jambon told public broadcaster VRT.

It has been claimed Cheurfi was making dark threats on messaging app Telegram before launching his attack on the Champs Elysees in Paris last night.

ISIS has claimed responsibility for the atrocity, which was carried out with a Kalashnikov weapon. A female foreign terrorist was also injured when a bullet ricocheted off the police car before Cheurfi was shot dead.

The fatal incident unfolded as presidential candidates, including National Front party leader Marine Le Pen, debated on a TV show nearby before Sunday's election.

French President Francois Hollande said he was convinced it was a terrorist attack, adding that he would hold a security cabinet meeting this morning.

The French-born killer lived in Chelles, a commuter town close to Paris in the Seine-et-Marne department.

In 2003 he was sentenced to 20 years inside a high security prison following the attacks in Roissy-en-Brie, also in Seine-et-Marne.

But he was let out early following an appeal ruling, giving him the freedom to carry out tonight's attack.

WHAT IS TELEGRAM? THE APP ALLEGEDLY USED BY KILLER The app makers have boasted of security settings which keep messages safe from 'snoopers' Telegram is a messaging app which focuses on speed and security, according to its makers. It allows users to send messages, photos, videos and files to groups of up to 5,000 and broadcast to unlimited audiences. A statement on Telegram's website about security says: 'Big internet companies like Facebook or Google have effectively hijacked the privacy discourse in the recent years. 'Their marketers managed to convince the public that the most important things about privacy are superficial tools that allow hiding your public posts or your profile pictures from the people around you. Adding these superficial tools enables companies to calm down the public and change nothing in how they are turning over private data to marketers and other third parties. 'At Telegram we think that the two most important components of Internet privacy should be instead: Protecting your private conversations from snooping third parties, such as officials, employers, etc

Protecting your personal data from third parties, such as marketers, advertisers, etc 'This is what everybody should care about, and these are some of our top priorities. Telegram's aim is to create a truly free messenger, without the usual caveats. This means that instead of diverting public attention with low-impact settings, we can afford to focus on the real privacy issues that exist in the modern world.' Advertisement

Cheurfi was the registered keeper of the grey Audi used in last night's attack. A raid on his home later found guns and ammunition, intelligence sources said.

He had targeted a parked patrol car full of traffic control officers working to the Paris prefecture.

The officer killed was at the wheel and was having an evening snack at the time of his death.

French television network BFMTV reports that Cheurfi had used the Telegram internet messaging service, which extremists have previously been claimed to favour because of its encryption.

Police are searching the home of the shooter in eastern Paris, and following the attack French presidential candidate Francois Fillon has called for the election campaign to be suspended.

Today a friend of Cheurfi's family said he was a recluse who blamed police for ruining his life.

Champs-Elysees killer Karim Cheurfi had been detained only last month, it has emerged, after informants said he was 'seeking to obtain weapons to kill policemen'

The 39-year-old did not attend formal mosque prayer services and became fascinated by jihadist propaganda via the internet, a confident of his mother claimed.

'Karim did not pray, he drank alcohol and watched jihadist propaganda, ' neighbour Hakim, 50, told MailOnline.

'He was not a good Muslim, he was a lost soul. He had no friends, no girlfriend, he never went out. He stayed at home all day watching stuff on the internet.

Another neighbour added: 'Karim didn't go to the mosque. He just stayed at home. You never saw him.'

Hakim continued: 'Karim blamed the police for ruining his life.

'He fired [a pistol] at police during a burglary and got sentenced to 15 years prison.

'He was only 20 at the time. He hated the police, he said they had ruined his life.

'He was "anti-cop". He would swear at officers in the street, call them b***ards. He didn't care.'

Hakim, whose family is close to Cheurfi's mother, said the gunman had only recently returned to the quiet residential street after spending years behind bars.

Cheurfi lived separately from his mother in a purpose-built apartment in the front of the property.

'He lived in the studio in the garden. The mother lived in the big house.'

Cheurfi's Algerian-born mother had divorced his father and had married a Frenchman with who she had second son. She later divorced her second son.

Detectives last night spent hours searching his modest home in the commuter town of Chelles, east of Paris.

Squadrons of heavily armed descended on the street in the early hours if the morning.

Intelligence sources said the dead assailant was a known radical on a so-called S-file, for 'State-security'

Police officers searched the home of the suspected gunman in east Paris following the attack in the capital on Thursday

Officers searched the home of the suspected gunman on Thursday evening after they travelled to his home in the east part of the capital

A third neighbour told MailOnline: 'I work nights so i got home at 3am and found police had blocked off the road.

'There were loads of cops. They were searching the house.

'Two officers escorted me to my house.'

The mother of two was not at home during the police raids. She is currently visiting relatives in the north of Algeria, Hakim claimed.

Other neighbours claimed that Cheurfi had a complicated family life.

'His parents split up but they stayed living at the same property,' one told MailOnline.

'The father Salat lived in the apartment in the front of the garden and the mother lived in the house at the back of the property.

'The mother married again, to a Frenchman, and they had a son together but the father stayed living at the property.

'So it was a bit complicated but that's life.

'Karim got on well with his half brother who is called Stephane.

'But he went to live in the apartment with his father when he got of prison.'

Another neighbor added: 'The mother is not here. She is in Algeria. She goes there every few months to visit relatives. She's not been well.'

Pierre-Henry Brandet, spokesman for France's Interior Ministry, confirmed that one police officer was dead and two seriously wounded following the 'targeted attack'.

He said a 'car pulled up just after 9pm' next to a police patrol car which was parked up on the busy avenue.

TIMELINE OF TERROR IN EUROPE The terrorist shooting in the centre of Paris is the latest deadly attack to hit western Europe in recent years. Here are some of the other atrocities. April 7 2017 - Stockholm A stolen truck was rammed into a crowd in Stockholm, killing four people and wounding 15. A 39-year-old Uzbek man confessed to the crime. Briton Chris Bevington, 41, who lived in Stockholm with his family and worked as a director with music streaming service Spotify, was among the victims. March 22 2017 - London Khalid Masood drove a hired car over Westminster Bridge, near the Houses of Parliament, mounted the pavement and hit pedestrians before crashing into railings outside Parliament. He stabbed PC Keith Palmer to death and also killed civilians US tourist Kurt Cochran plus Britons Aysha Frade and 75-year-old Leslie Rhodes. March 18 2017 - Paris An attacker with an automatic weapon opened fire on police in Paris' Champs-Elysees shopping district, killing one officer and wounding another before police shot and killed him. February 3 2017 - Paris A machete-wielding man shouting "Allahu akbar" attacked French soldiers guarding the sprawling building at the Louvre museum. The suspect, who was shot four times, was later named by officials as Egyptian Abdullah Reda Refaie al-Hamahmy, 28. December 19 2016 - Berlin A truck ploughs into a crowded Christmas market in central Berlin, killing 12 people and injuring 48. July 26 2016 - Saint-Etienne-du-Rouvray Two attackers killed 85-year-old parish priest Father Jacques Hamel with a blade and seriously wounded another hostage in a church in northern France before being shot dead by French police. The two hostage-takers had pledged allegiance to Islamic State, French President Francois Hollande said. The men arrived as Fr Hamel was leading morning mass in Saint-Etienne-du-Rouvray, a working-class town near Rouen, northwest of Paris. July 24 2016 - Ansbach A Syrian suicide bomber injured 15 people when he blew himself up outside a music festival. The suspect, named by officials as 27-year-old failed asylum seeker Mohammad Daleel, 27, had pledged allegiance to Islamic State, had a history of mental illness and faced deportation to Bulgaria. The terror group claimed responsibility for the attack, saying the bloodshed was carried out by "one of the soldiers of the Islamic State". July 18 2016 - Munich An 18-year-old German-Iranian gunman, who was not known to police, opened fire at a crowded shopping centre and fast-food restaurant in Munich, killing nine people and injuring 16, including children. July 14 2016 - Nice A truck ploughed into Bastille Day revellers in the southern French city of Nice, killing 86 people. IS claimed responsibility for the attack, which was carried out by a Tunisian living in France. June 14 2016 - Paris A police commander and his partner were found dead outside his home in the Paris suburb of Magnanville. The French suspect declared his allegiance to Islamic State leader Abu Bakr al-Baghdadi and threatened to kill non-believers, according to Paris prosecutor Francois Molins. March 22 2016 - Brussels Three IS bombers killed 32 people at Brussels airport and subway. The blasts took place during the morning rush hour. The bombers were all Belgian. November 13 2015 - Paris Suicide bomb-and-gun attacks killed 130 people at various entertainment hotspots in Paris. More than 360 people were wounded. IS claimed responsibility. January 7-9 2015 - Paris Bloodshed was brought to Paris by gunmen who launched three days of attacks in the capital and its surrounding regions. The massacre started with an attack at the offices of satirical magazine Charlie Hebdo, killing 17 people. It ended with a huge police operation and two sieges. During the bloodshed, another militant killed a policewoman and took hostages at a supermarket on January 9, killing four before police shoot him dead. Advertisement

A man jumped out with a weapon and started firing indiscriminately into the police vehicle, hitting the unidentified officer who died directly in the head.

The assailant then ran off, pursued by other officers. Two of them were wounded as they killed him.

Mr Brandet said 'all lines of investigation were being pursued', while intelligence sources said the dead assailant was a known radical on a so-called S-file, for 'State-security'.

This means he would have been under surveillance, because he was a known risk to the country.

Mr Brandet later said a possible accomplice had turned himself over to Belgian police, but it was 'too early to say' if he had played a significant part in the attack.

President Hollande, speaking from the Elysee palace close to the scene of the shooting, said: 'A national tribute will be paid to this policeman who was killed in such a cowardly way.

'A passerby was hit. The assailant was neutralised by other police officers. The entire area has been cordoned off. The people present have been evacuated.'

Mr Brandet said the assailant who opened fire on a Paris police van was armed with an automatic firearm akin to a 'war weapon'.

He refused to give any specific detail about the suspect's possible criminal history or affiliations.

Armed officers rushed to the scene of the killing, and Metro stations were closed in the aftermath of the attack.

A spokesman for the police said the attacker targeted officers guarding the area near the Franklin Roosevelt subway station at the centre of the popular shopping district.

There was a huge police response to the killing in Paris this evening, with roads around the Paris landmark closed

Officers at the scene of tonight's attack, which claimed the life of one of their colleagues