A Japanese nuclear power plant operator Tuesday reported a small leak of radioactive water, amid growing public concern about the country's nuclear industry.

About 200 litres (52 gallons) of water leaked from a tank in a building adjacent to a reactor facility at the Satsuma Sendai plant on the southern island of Kyushu, a spokesman for Kyushu Electric Power said.

The leak was contained within the building and there was no risk to the local environment, he said, adding that the plant continued to operate normally.

The cause of the leakage has yet to be determined.

The incident comes amid public nervousness over the country's nuclear industry after a fire and leaks at a sprawling nuclear power plant in central Japan in July due to a powerful earthquake.

Japan, which has virtually no natural energy resources, relies on nuclear power for about one-third of its power needs.