Some 40 Greenpeace activists were arrested inside an atomic power plant in Argentina on Monday at a protest on the second anniversary of the earthquake and nuclear disaster in Japan, the group said.
The protesters "were beaten and detained after entering the Embalse nuclear facility in Cordoba" some 700 kilometers (450 miles) northeast of Buenos Aires, a Greenpeace statement said.
It added that the group had hoped to underscore the dangers of nuclear power, two years after a 9.0-magnitude earthquake and resulting tsunami struck the city of Fukushima.
Media reports said that once inside the Argentine plant, the protesters unfurled a huge banner that read: "Nuclear Danger Must End."
The activists mocked the security at the site, saying they encountered little difficulty in getting inside the facility to hold their demonstration.
The Japan quake two years ago unleashed a giant tsunami along the northeastern Pacific coast that killed nearly 19,000 people and crippled reactors at the Fukushima Daiichi nuclear plant, which went through meltdowns and explosions, spewing radioactive materials into surrounding areas.
The Fukushima accident forced tens of thousands of residents near the area to abandon their homes and jobs in heavily contaminated areas.