Greenpeace said Thursday it had launched legal action to demand that Switzerland shut down Beznau, the world's oldest commercial nuclear plant, for security reasons.
The plant, located in the northern Swiss canton of Aargau, near the German border, has been running for 46 years.
"The Beznau nuclear plant would not resist a powerful earthquake," the environmental protection group said in a statement.
The organisation said it, along with the Swiss Energy Foundation and the Tri-national Nuclear Protection Association, had filed the suit on Wednesday demanding "the definitive closure of the installation."
Following the 2011 Fukushima nuclear disaster in Japan, Swiss authorities launched probes to determine how all of the country's four nuclear power plants would withstand an earthquake.
In July 2012, they determined that all were fit to withstand a severe earthquake, and could keep running since they posed no threat to the population or the environment.
But Greenpeace and the other plaintiffs in the case said the experts' calculations were based on erroneous technical norms.
The organisations said they had asked in a letter that the Federal Inspectorate for Nuclear Safety (IFSN) "correct its July 2012 decision and order the closure of the Beznau plant."
If the IFSN maintains its decision, it should announce this publicly, Greenpeace said.
The plaintiffs would then take the case to a federal administrative court, and if necessary all the way up to the supreme court, it said in a statement.
Beznau, which opened in 1969 and counts two reactors that are currently undergoing repairs, became the world's oldest nuclear plant after the 2012 closure of Britain's Oldsbury reactor.
Switzerland is considered to have only a "moderate" earthquake risk, but some 10,000 quakes that have hit the Alpine country since the 13th century, and 12 have caused significant damage, according to seismologists.
The most powerful earthquake in Swiss history hit Basel in 1356, measuring 6.6 on the Richter scale and levelling a large part of the city.
Explore further: Swiss environmental groups want Beznau nuclear plant shut