A Japanese nuclear reactor near a fault line must remain shut because of the risk of its being struck by earthquakes and volcanic eruptions, a high court ordered on Friday.
All nuclear power stations were shut down after the 2011 Fukushima nuclear accident following a catastrophic tsunami, and many remain closed.
The Japanese public has turned against atomic power, despite Prime Minister Shinzo Abe insisting the nation needs nuclear plants to power the world's third-largest economy, and the court decision was a boost for the country's anti-nuclear movement.
The move by the Hiroshima High Court reversed a lower court decision in March that would have allowed the reactor at the Ikata nuclear plant in western Japan to resume operations.
The plant's operator, Shikoku Electric Power, wanted to resume work at the reactor, which had been halted for routine inspections, and said it will appeal the high court's ruling.
The case was originally lodged by residents of a neighbouring region who complained the utility failed to properly evaluate the risks posed by a local volcano and seismic faultlines.
High court presiding judge Kazutake Mori revoked the lower court ruling that paved the way for the reactor to come online.
Mori said there was an active fault line near the plant and safety assessments had been insufficient, national broadcaster NHK said.
He also argued it was not logical to assume that volcanic eruptions can be predicted far in advance, as assumed under the national standards for operating nuclear reactors, according to NHK.
"There is a fault line within two kilometres from the nuclear plant but Shikoku Electric has not conducted thorough surveys, and the way the Nuclear Regulation Authority reached its assessment that there was no problem contained errors and inadequacies," the judge said, according to NHK.
Shikoku Electric criticised the ruling and stressed the scientific merit of the firm's argument that it was safe to operate the reactor.
"After closely examining the decision, we will file a petition of objection so that the injunction will be cancelled as soon as possible," the utility said in a statement.