France attack: Killer sent gruesome selfie with severed head on Whatsapp

The killer decapitated his boss in an attack on a gas factory in France

The man suspected of decapitating his boss in an attack on a gas factory in France has confessed to the grisly crime, sources close to the investigation said today.

Yassin Salhi, 35, "has also given details about the circumstances" surrounding the killing, according to the sources, who said he would be transferred to Paris for further questioning later today by anti-terrorist police.

Salhi's confession came after it emerged the married father-of-three sent a gruesome selfie photo of himself and the severed head to a WhatsApp number in Canada.

Investigators have warned however that it could be a relay number and the intended recipient could be anywhere in the world.

After several hours of silence, Salhi has begun to open up to investigators about the assault, which came six months after 17 were killed in Islamist attacks in Paris that began with the Charlie Hebdo massacre.

On Friday morning, Salhi rammed his van into the US-owned Air Products factory near France's second city of Lyon in what President Francois Hollande said was a "terrorist" attack designed to blow up the whole building.

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.

Police then made the grisly discovery of the severed head of Salhi's boss, 54-year-old Herve Cornara, lashed to the gates of the factory near two flags on which were written the Muslim profession of faith.

Prime Minister Manuel Valls repeated that 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 rolling news channel.

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

It's not a question of whether there will be another attack, but "when" and "where", stressed Valls.