A nuclear reactor in Sweden was stopped on Thursday after the country's nuclear industry watchdog said the operator had failed to comply with its safety requirements, safety officials said.

The Oskarshamn plant's number two reactor was taken out of service after the operator was unable to show the Swedish Radiation Safety Authority that standard maintenance work had been performed on two diesel generators used for emergency power supply.

The situation was not urgent, said Leif Karlsson, head of section at the agency.

"With systems that are often on stand-by, it's extra important to perform the necessary maintenance work," he said.

Oskarshamn is operated by OKG, which is owned by Germany's Eon and Finland's Fortum group.

"OKG has not been able to show that parts of the equipment that is essential to guaranteeing a safe operation fulfill the authority's requirements for operational readiness and reliability," the radiation safety agency said in a statement.

Oskarhamn, on the east coast of Sweden, around 300 kilometers (180 miles) south of Stockholm, is one of Sweden's three nuclear power plants.

The plants have 10 nuclear reactors and the country's parliament passed a landmark bill in June 2010 allowing them to be replaced at the end of their life spans, instead of simply ending nuclear power when they expire.

Some 35 percent of electricity in Sweden is generated from nuclear power.