STOCKHOLM -- Swedish police arrested four activists on Wednesday after they spent 28 hours hiding in the grounds of a nuclear power station in southwestern Sweden. Greenpeace said two other anti-nuclear protesters left on their own after hiding at another plant on the eastern coast.
Nuclear power officials said the activists were in the outer perimeters of the nuclear power stations and posed no security threat. The campaigners say they were trying to highlight what they say is poor safety at Swedish nuclear sites.
The four demonstrators were among some 20 people who forced their way into the Ringhals reactor site on Tuesday morning by breaking chains on an outer perimeter gate. Fifty others scaled the outer fences of the Forsmark reactor site, Greenpeace said. Most of the activists were detained soon after illegally entering the enclosures, the environmental group said.
Two people remained at the Forsmark site even after the detentions, said Greenpeace spokeswoman Birgitte Lesanner said. Greenpeace said in a statement late Wednesday that the two had left of their own volition. It was unclear whether they were later detained.
"It just goes to show how bad the security is," Lesanner said.
She said some activists cycled into the fenced-off outer perimeter of one of the plants, and that recent European Union stress tests on nuclear facilities should have paid more attention to whether access to the plants is secure. "People can just go in, like we did on bikes," she said.
Nuclear power officials maintain that the campaigners did not pose a safety risk by entering the low -security area.
"It's an industrial area like any other industrial area with a fence. It's a big area, 50-60 hectares (120-150 acres) with some buildings, warehouses, lots of trees and unused land," Ringhals spokesman Gosta Larsen said. "It's prohibited to stay inside the private area without a permit, but they did not compromise security at all."
The activists did not enter the high-security zone _ the closely monitored area where the reactors are situated, surrounded by multiple fences, alarms and gate guards.
Police in the Ringhals region said Wednesday they were holding four activists on suspicion of aggravated illegal entry, after releasing most of the 18 protesters they initially detained on Tuesday.
Sweden has 10 nuclear reactors at the country's three power plants: Ringhals, Forsmark and Oskarshamn _ providing about half of the country's electricity.
Its nuclear industry has come under fire for the lack of safety precautions. In June, a small amount of explosives was found on a forklift at the Ringhals plant but officials were unable to say how it got there.
Last year, a fire broke out in a Ringhals reactor after staff had left a vacuum cleaner in the containment building.
In 2010, Greenpeace activists broke into the Forsmark power plant site by climbing a fence and staged a demonstration.