French police arrested three Greenpeace members Wednesday after an activist flew into the grounds of a nuclear power plant using a paraglider in a stunt aimed at revealing alleged security flaws.

The environmental group said it wanted to "send a message" to Francois Hollande and Nicolas Sarkozy as the two presidential candidates prepare for Sunday's election.

Two men were detained after the paraglider incident at the Bugey plant in southeastern France while a third was arrested after he sneaked in through a truck entrance to the Civaux nuclear plant in the west of the country.

"A Greenpeace activist arrived with a motorised paraglider around 7:40 am (0540 GMT). He flew over the plant, threw a smoke bomb and landed inside, where he was detained," police said.

Greenpeace said the detained activist was a German national.

The second person was arrested outside the plant on suspicion of helping guide the pilot, police said.

Greenpeace spokeswoman Sophia Majnoni said the protests were designed to "send a message to the two candidates in the presidential election who are denying the risk of nuclear power".

"We wanted to illustrate an external danger, like a fall of an airplane" into a nuclear plant, she said.

EDF, the French energy giant that runs the country's nuclear plants, said in a statement that the safety of the Bugey plant was at no time compromised by the stunt.

In December, Greenpeace activists broke into two nuclear power plants in France in an action the group said was aimed at exposing the vulnerability of the facilities.

Nine activists broke into the Nogent-sur-Seine plant near Paris and two into the Cruas plant in southern France.