French police have arrested at least 29 Greenpeace environmental activists who broke into a nuclear plant.
Greenpeace said the activists reached the walls of the reactors in the Tricastin plant in southern France.
However the interior ministry said the protesters, in several groups, did not reach the most secure areas.
The activists projected huge anti-nuclear slogans onto the outside walls. Most of France's electricity comes from nuclear power.
Tricastin is in the town of Pierrelatte, some 200km (120 miles) north of Marseille.