Anti-nuclear protestors have called for the immediate shutdown of the Mühleberg power plant outside the capital, Bern.
The demonstrators gathering at the site of the plant on Monday said serious safety risks of the reactor were threatening more than half a million residents in the region.
Speakers said it was a scandal that the authorities continued to ignore reality and had no emergency evacuation plans in case of a disaster at the controversial plant, which has been on the electricity grid since 1972.
“Fukushima can no longer be decommissioned – but let’s shut down Mühleberg” a protest banner read.
Organisers of the protest said up to 3,500 people had travelled to Mühleberg by bicycle, on foot or with public transport from nearby towns and cities.
Three weeks ago, around 20,000 demonstrators gathered in northern Switzerland in one of the largest anti-nuclear protests in decades.
Last week parliament began discussing a government proposal to decommission the country’s five nuclear power reactors by 2034 and boost renewable energy resources.
swissinfo.ch and agencies