STRASBOURG (REUTERS) - Environmental activists from Greenpeace entered a nuclear power plant operated by EDF in Fessenheim, eastern France, on Tuesday, demanding European governments cut the use of nuclear energy, the group said.

Greenpeace said that more than 60 people of 14 nationalities had entered the plant, France's oldest. Firefighters confirmed activists had broken into the site. Other authorities declined to comment.

There was no indication that power output from the plant had been interrupted, according to the website of the RTE electricity network operator.

President Francois Hollande has promised to close Fessenheim by 2016 and cut France's reliance on nuclear energy to 50 per cent of its electricity mix from 75 per cent now.

"The Fessenheim plant is a symbol," Greenpeace activist Cyrille Cormier said in a statement. "Its planned closure must be the beginning of a series of plant closures in Europe to limit the accidental and financial risks linked to ageing (plants) and to start the energy transition."

The activists hung a banner from the roof of the plant that said "stop risking Europe" and called on Hollande and German Chancellor Angela Merkel to commit at an EU summit on Thursday to generating energy from alternative sources.

Greenpeace activists have a history of breaking into nuclear plants in France and about 30 were arrested last July after entering EDF's Tricastin plant in southern France.