A suspected Islamic terrorist accused of carrying out an attack in France in which a man was decapitated was known to police, authorities have revealed.
The victim’s severed head was found stalked on a gate at the entrance of a gas factory in Grenoble, on the outskirts of Lyon, with a message written on it, reportedly in Arabic.
French officials said two men in a car had earlier crashed into the factory site and ploughed into gas canisters, sparking an explosion, at around 10am local time.
Two other people were injured in the incident which French president Francois Hollande described as having “all the hallmarks of a terrorist attack”.
The victim’s torso was found close to the factory site, while two flags - one white and one black and both with Arabic inscriptions - were discovered at the scene, a security official said.
The victim has not yet been formally identified but local media reported that he was a transport manager who was at the factory for a delivery.
One of the suspected attackers - a 30-year-old man - has been arrested after he was detained by a firefighter.
French interior minister Bernard Cazeneuve said the suspect had been under investigation for possible ties to Islamic extremists in 2006, but surveillance was dropped in 2008.
A number of other people are in custody, he added.
President Hollande, who is travelling back to France from Brussels, said there was “no doubt” the terrorists meant to cause an explosion at the factory using gas cannisters.
France would “never give into fear” and the attack must not “create unnecessary division”, he added.
Mr Cazeneuve said authorities were searching for possible accomplices.
A spokesman for Air Products, which runs the factory, said: “Our priority at this stage is to take care of our employees, who have been evacuated from the site and all accounted for.
“Emergency services are on site and have contained the situation. The site is secure. Our crisis and emergency response teams have been activated and are working closely with all relevant authorities.”
Prime Minister David Cameron expressed his sympathies over the incident to president Hollande.
The two leaders spoke in Brussels, where they are attending a European Council summit.
A Downing Street spokeswoman said: “He expressed his sympathies for what looks like an appalling incident.
“Details are still emerging, so we wait to see those. But it clearly looks an extremely concerning situation and our thoughts are with all those affected by it.”
Asked whether Britain was taking additional security measures in response to the attack, the Number 10 spokeswoman said the authorities were “looking at the situation closely” but had nothing further to add.
France went on high alert in January after extremist brothers Said and Cherif Kouachi killed 12 people - including two police officers - in attacks on satirical magazine Charlie Hebdo in Paris.
Mr Cazeneuve said one of the suspects in custody is thought to be Yacine Sali, who was previously investigated for “radicalisation charges”.
A woman claiming to be the suspect’s wife called French radio station Europe 1 in which she insisted the family were “normal Muslims”.
“My heart is going to stop,” she said. “I do not know what has happened. Have they arrested him?”
The woman said her husband - a father-of-three - went to work as a delivery driver at 7am and she expected him home in the afternoon.
She added: “We are normal Muslims. It is Ramadan. We have three kids and a normal family life.
“Who can I call to give me more information because here I do not understand?
“I’m afraid to do anything.”
A second suspect was arrested at his home in Saint-Quentin-Fallavier, according to French media reports.