The ISIS fanatic accused of beheading his boss has 'confessed' to his grisly crime and blamed it on 'problems at home and work'.

Yassin Salhi, 35, told investigators he decapitated Herve Cornara because of the 'personal difficulties' in his life.

His confession comes after it emerged the married father-of-three sent a macabre selfie of him posing with the severed head of his boss reportedly daubed in Islamic writing to a WhatsApp number in Canada.

Terror suspect Yassin Salhi returns to his apartment with Special Forces, in Saint-Priest, France

French police escort Yassin Salhi, who is accused decapitating his boss in an attack on a gas factory, as they leave his flat in Saint-Priest

Covering his face and wearing a pair of three-quarter length Adidas shorts, Salhi is marched away by police

Salhi is accused of decapitated Herve Cornara because of the 'personal difficulties' in his life

Salhi wears protective clothing and covers his face as he returns to his apartment with French special forces

Investigators said it was not possible to fix the location of Salhi's contact, but it has been reported the recipient was in Syria where ISIS has seized swaths of territory.

A glimpse of his bearded face can be seen beneath a white piece of cloth covering his head as he visited his apartment in Saint Priest with members of France's Special Forces on Sunday.

He was handcuffed and pictured wearing protective clothing as heavily armed officers flanked him from both sides.

Herve Cornara was the boss at ATC-colicom in Chassieu, France. His severed head was found surrounded by ISIS flags on Friday

Cornara's head was found pinned to the gates at the American-owned Air Products factory in Saint-Quentin-Fallavier near Lyon, surrounded by two Islamist flags, on Friday morning.

A knife and a fake pistol were also discovered nearby.

He had been strangled before he was decapitated.

Salhi told investigators he killed Cornara in a car park and took a picture of him posing with the severed head.

He then drove his van at high speed into warehouse packed with inflammable chemicals where he attempted to cause an explosion.

He was overpowered by a firefighter as he was trying to prise open a bottle of acetone in an apparent suicidal bid to destroy the factory.

A testimony by a friend of the victim reported by Le Figaro daily suggested Salhi and his boss had several heated arguments.

Other local media cited his former martial arts instructor as saying the otherwise calm Salhi was subject to such outbursts of rage that other pupils would refuse to spar with him.

That the suspect gave the killing the appearance of an Islamist strike is so far not sufficient to convince investigators he was motivated by a jihadist ideology.

A source close to the investigation said: 'We don't know whether we're dealing with a fundamentalist who flipped or a real terrorist. Investigators are wondering whether this isn't just a simple criminal act.'

Suspect Yassin Salhi said he killed Cornara (pictured) in a car park before his corpse was dumped at the Air Products factory site in Saint-Quentin-Fallavier and his head impaled on a fence 30 feet away

A French flag and flowers are placed on the fence of the Air Products gas factory where the severed head of Cornara was found

This is the apartment block of Salhi - his wife, sister-in-law and mother remained in police custody yesterday but they are not, at this stage, regarded as suspects

This is the front door of Salhi, who is accused of decapitating his boss on Friday in a horrifying attack

Salhi - who is understood to have been known to security services since at least 2006 - reportedly told arresting officers he is a member of the Islamic State terror group.

He is thought to not have had a criminal record and an investigation into his 'possible radicalisation' was dropped in 2008.

Sources close to the investigation said Salhi was radicalised more than a decade ago after contact with Muslim convert Frederic Jean Salvi - known as 'Ali' - who is suspected of preparing attacks in Indonesia with Al-Qaeda militants.

Sickening: The victim's head was found hanging on a fence near the factory's entrance. Two homemade Islamist flags - one white and one black, both with Arabic inscriptions - were found alongside it

Terror raid: French special forces escort an unidentified woman and child as they leave Yassin Salhi's apartment building today - they remain in police custody

Speaking before the raid on her home, Salhi's wife described her husband as a 'normal Muslim' who left for work as usual at 7am this morning. 'My heart stopped when I heard he was a suspect....I expected him this afternoon,' the unnamed woman told French radio station Europe 1.

She added: 'My sister said turn on the television. She was crying... I know my husband. We have a normal family life. He goes to work, he comes back...We are normal Muslims. We do Ramadan. We have three children and a normal family life.'

His wife, sister-in-law and mother remained in police custody yesterday but they are not, at this stage, regarded as suspects.

A fourth person arrested on Friday was released without being charged. Under French anti-terrorism laws, Salhi and the women can be held for up to four days before either being released or handed preliminary charges.

Location: The attack took place in Saint-Quentin-Fallavier, close to the city of Lyon in the south east of France

The attack came only six months after 17 people were killed in Islamist attacks in Paris that began with the Charlie Hebdo massacre.

Prime Minister Manuel Valls said today the world was engaged in a 'war against terrorism'.

'We cannot lose this war because it's fundamentally a war of civilisation. It's our society, our civilisation that we are defending,' Valls told iTELE news channel.

France is facing 'a major terrorist threat' which needs to be fought 'over the long-term', he warned.

There are 1,573 French nationals or people resident in France 'listed as being implicated in terrorist networks.'