A man with suspected ties to Islamic State extremists who is accused of beheading his boss at a French gas factory is facing preliminary charges of murder and terrorism links.

Yassin Salhi was arrested after the attack on Friday, in which he also tried to cause an explosion by crashing his delivery truck into gas canisters.

His lawyer says Salhi said he was acting purely for personal reasons when he decapitated his boss after being reprimanded.

Prosecutor Francois Molins said on Tuesday that Salhi had a history of radical Islamic ties dating back to 2003.

Preliminary charges under French law mean that investigators have a strong reason to suspect involvement in a crime, and give them more time for deeper investigation before deciding whether to send the case to trial.

Salhi, a truck driver with a history of radical Islamic ties dating back to 2003, was seized by firefighters at the Air Products chemicals warehouse.

According to Mr Molins, Salhi has denied he was motivated by terrorism and said he neither remembers the beheading nor sending any photos.

"According to him his motive was only personal and not terrorist. One does not exclude the other,"Mr Molins said.

"He decapitated his victim, he hung the head on a chain, and he wanted to get the maximum publicity possible."

Mr Molins has requested preliminary terrorism charges to be filed against Salhi and has opened a formal terrorism investigation, including into his ties with the man in Syria, identified as Sebastien Younes.

Mr Molins said investigators recovered a message in which Younes appeared to be claiming responsibility for inspiring his friend.

Air Products officials said Salhi had an entry badge for the site in Saint-Quentin-Fallavier, and had never caused problems in the past.

Mr Molins said Youens, who has been in Syria since November, was in contact with IS chiefs about the photos.

The attack on Friday came days after IS militants urged followers to strike during the Muslim holy month of Ramadan.