A device has exploded close to the entrance of the Mont Blanc tunnel linking France and Italy, only hours before it was due to be reopened to cars.
The explosion damaged a car parked on the French side of the tunnel but caused no injuries. The tunnel has been closed for almost three years, since a fire swept through it and killed 39 people.
Environmental groups and local people have been protesting against the planned resumption of heavy goods traffic on the route later this month.
