A gruesome selfie emerged from the France terror attack and was sent to a Canadian phone, according to reports.

A trans-Atlantic operation between Canadian and French authorities has been launched to track down the destination phone.

The picture was purportedly taken by an Islamist suspected of decapitating his boss in France. The man, as well as his wife and sister, are in custody.

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Herve Cornara, who was found beheaded and pinned to the fence of a chemical factory. Photo: AAP

Sources close to the investigation into Friday’s attack near Lyon say Yassin Salhi, a 35-year-old married father of three, sent a picture of himself with the severed head via the WhatsApp messaging service to a Canadian number.

“Though I can’t comment on operational aspects of national security, I can say that we are helping French authorities in their investigation,” said Jean-Christophe de Le Rue, spokesman for Canadian public safety minister Steven Blaney.

The message was sent to a Canadian number, but investigators said they were still working to determine the final recipient, as the number used could be a relay to another phone in another location.

Authorities are questioning Salhi about Friday’s attack, during which he also drove his van into a warehouse packed with dangerous gases in an apparent bid to blow up the factory and himself.

The attack came on a day when nearly 70 were killed across three countries in separate terror attacks: on a beach in Tunisia and another at a mosque in Kuwait.

– with AAP