A decapitated body covered in Arabic writing was found at a U.S. gas company in southeast France on Friday, police sources and French media said, after an assailant rammed a car into the premises, triggering an explosion.

The attacker survived the blast and was arrested. The identity of the beheaded victim was not clear but French media said it was a manager at a local transport company, on the site for a delivery.

Speaking from a European Union summit in Brussels, French President Francois Hollande described it as a terrorist attack and said all measures would be taken to stop any future strikes on a country still reeling from Islamist assaults in January.