Greenpeace demonstrators chained themselves to a truck near a nuclear treatment facility in western France Tuesday in a bid to stop an imminent shipment of US military-grade plutonium reaching the plant, resulting in several arrests.
Police and firemen took two hours to cut loose the dozen protesters who had attached themselves under and inside the vehicle, which had the words "Stop Plutonium" written on its side next to a nuclear symbol.
The truck itself was immobilised by a big metal slab, blocking the road leading to the Cogema nuclear recycling facility in La Hague, near the town of Cherbourg.
Greenpeace members said all of those who took part in the protest were arrested.
A spokeswoman for the state-owned plant, Laurence Pernod, criticised the action as "a media-seeking gesture designed to fool the public".
She added: "We don't understand how a militant organisation that has always been against nuclear weapon proliferation could rise up against an operation meant to neutralise them."
Two British-registered vessels carrying 140 kilograms (308 pounds) of plutonium from US weapons arsenals were expected to dock in Cherboug after a voyage from North Carolina.
The plutonium is to be taken to the French nuclear reconditioning plant at La Hague, then sent to a facility in southern France to be recycled and eventually returned for civilian use in the United States.
One Greenpeace militant at the protest, a German named Thomas Breuer, said the organisation wanted "to focus attention on this very dangerous and completely unnecessary transport."
Greenpeace has said the long distances of road transport involved constituted "considerable" risk, not least because the cargo's containers could easily be opened by shoulder-launched rockets.
Authorities have kept the docking date and hour a strict secret, citing security reasons, and forcing protesters to hold all-night vigils at the port.
At a court hearing later Tuesday the French nuclear processing company Areva was hoping to gain an injunction banning Greenpeace activists from approaching the vessels or overland convoy.
The court action came after police on the weekend broke up a Greenpeace flotilla and arrested three activists, who were released Monday.