Smoke rose Thursday from the world's largest nuclear power plant in Japan, which was shut down by an earthquake two years ago, but the operator said no-one was injured and there was no radiation leak.

The smoke was caused by friction from the brake of a crane in a reactor's turbine room, operator Tokyo Electric Power Co. (TEPCO) said in a statement.

"We reported immediately to the fire station and used fire extinguishers and now the smoke has stopped," the statement said.

"There were no injuries nor any radiation leak" in the Kashiwazaki-Kariwa nuclear plant in Niigata prefecture, 200 kilometres north of Tokyo, it said. The company said it would thoroughly investigate.

Kashiwazaki city was rocked by a 6.8-magnitude earthquake in July 2007. The epicentre was just 16 kilometres from the plant, where a fire started and a small amount of radiation leaked out, leading to the plant's shutdown.

The operator has been running check-ups this year to restart commercial operations at the power plant.

Residents have voiced safety fears following a string of fires there as well as concerns raised by some geologists that an off-shore tectonic faultline could trigger stronger earthquakes in future.

Japan, the world's second largest economy but with virtually no energy deposits of its own, relies on nuclear power for about one-third of its electricity demand and aims to boost the figure to 40 percent by 2010.