Two British-registered vessels carrying 140 kilograms (308 pounds) of plutonium from US weapons arsenals were expected to dock here after a voyage from North Carolina.

Authorities 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 ecology watchdog Greenpeace from demonstrating any nearer than 100 metres (yards) from the vessels in dock, at less than 300 metres at sea inside French territorial waters, and at less than 100 metres from the overland convoy scheduled to convey the plutonium through France, Greenpeace said.

Some of the many anti-nuclear proteesters gathered here were nonetheless exploring the possibility of some kind of protest action, to be planned with the greatest discretion so as not to alert authorities.

"We are closely studying the possibility of taking action, but we can't say anything in advance, especially not over the phone," activist Philippe Le Marechal, coordinator for the anti-nuclear flotilla here told AFP.

While the local authorities were playing their cards equally close to their chests, giving no indication as to the arrival time of the controversial cargo, the protesters were on high alert Tuesday for the slightest indication of the imminent arrival of the two British-registered vessels carrying a shipment of 140 kilograms (308 pounds) of plutonium from US weapons arsenals after a two-week voyage from North Carolina on the east coast of the United States.

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.

Three Greenpeace activists in a flotilla protesting the shipment were released from police custody Monday.

They included French yachtsman Eugene Riguidel, whose sailboat was impounded by the police.

Riguidel's boat was boarded after it touched buoys marking the military zone.

The crew -- Riguidel, Jonathan Castle, first captain of the Greenpeace ship Rainbow Warrior, and Pernilla Svenberg of Greenpeace International in Amsterdam -- were taken into custody for 24 hours.

Protesters have also taken up position along the land route to be followed by the road convoy to the plant at La Hague.

Banners proclaimed "Stop plutonium."

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