Sixty protesters, wearing bright yellow raincoats, gathered outside the entrance Garona power plant, located some 350 kilometres (220 miles) north of Madrid, just before dawn, according to Spanish television.

Several chained themselves to the gates of the facility, others sat in the road leading into the plant while eight activists barricaded themselves inside a container set up in front of the entrance.

Police moved in some 10 hours after the protest began to clear the entrance to the plant, which a spokesman said continued to operate normally throughout the day despite the demontration.

Nuclear power is highly unpopular in Spain and Prime Minister Jose Luis Rodriguez Zapatero has vowed to gradually phase out nuclear power as part of a drive to boost reliance on renewable energy sources like wind and solar power.

But as oil prices hit record levels earlier this year, the government has not ruled out extending the working lives of Spain's existing eight nuclear power plants which supply about 20 percent of Spain's electricity needs.

"Zapatero would make a big mistake if he decides to turn his back on the anti-nuclear majority," said the director for the Spanish arm of Greenepace, Juan Lopez de Uralde.