Details remain sketchy at this stage but here are the main points:

  • A decapitated head covered in Arabic writing has been found at a US gas company at Saint-Quentin-Fallavier near Grenoble
  • The suspect entered the factory and set off several small explosive devices, sources say
  • Police say it is unclear whether the attacker acted alone or had accomplices
  • A suspect has been arrested, reports say, and it is believed he was known to security services
  • Prime minister Manuel Valls orders increased security measures at all sensitive sites in the area