TOKYO (BLOOMBERG) - A Japanese court overturned a ruling that allowed a nuclear reactor in the country's south to operate, frustrating the government's push to bring online dozens of plants shut in the wake of the 2011 Fukushima disaster.

The decision by the Hiroshima High Court, which cited risks from nearby volcanoes, sides with local citizens and reverses a lower court's ruling that had cleared the way for Shikoku Electric Power Co to operate its Ikata No. 3 unit, according to an emailed statement Wednesday (Dec 13) from the company.

The reactor, which restarted last year under stricter safety regulations, has been shut for maintenance and was scheduled to restart on Jan 20.

Shikoku Electric fell as much as 11 per cent in Tokyo, the biggest decline in more than four years, before paring the drop to 8.3 per cent.

The injunction issued by the court is a blow to Prime Minister Shinzo Abe's goal of having nuclear power account for as much as 22 percent of the nation's electricity mix by 2030.

Public opposition through local courts and municipal governments has emerged as one of the biggest obstacles to that plan. Just four of Japan's 42 operable nuclear reactors are currently online.

The ruling was the first time a high court in Japan has overturned a lower court on the issue of nuclear restarts since the Fukushima disaster. A district court in Hiroshima sided with the utility in March in deciding not to issue a temporary injunction.

Shikoku called Wednesday's (Dec 13) ruling "unacceptable" and said it will try to get it reversed. The injunction is effective through Sept 30, 2018, according to court documents.

The Hiroshima High Court said risks from volcanoes weren't being "rationally evaluated" by the Japan Nuclear Regulation Authority. The agency declined to comment because it was not involved in the court case.