A Japanese court on Wednesday ordered two regional nuclear reactors to shut down over safety concerns, the plant's operator said, just days before the fifth anniversary of the Fukushima nuclear disaster.
The order would bring the number of operating reactors in Japan down to two. Dozens were shut down in the wake of the accident.
The ruling is the first to require the shutdown of reactors that were restarted under stricter safety standards adopted after the 2011 accident, the worst atomic crisis in a generation.
The ruling from the Otsu District Court - which sided with area residents who launched their legal action claiming the reactors posed safety risks - is a blow to Prime Minister Shinzo Abe's bid to bring back nuclear power.
The reactors ordered to be shuttered are Kansai Electric's No. 3 and No. 4 reactors at its Takahama nuclear plant, some 350 kilometres (215 miles) west of Tokyo.
The No.4 reactor was taken offline last month due to an unexpected technical glitch days after it restarted, while the No. 3 reactor is currently operating.
Kansai Electric said it would respect the "extremely regrettable" decision and shut down operations. But it said it would appeal.
"This court order is not something the company can accept," it said in a statement.
After the order was handed down Wednesday, television footage showed plaintiffs and local residents cheering and holding banners celebrating their victory.
Two reactors in the southern prefecture of Kagoshima, operated by Kyushu Electric Power, restarted in August and October last year, ending the two-year hiatus in nuclear power generation.
A pair of reactors were briefly switched on again after the accident but were then shuttered.
Anti-nuclear sentiment still runs high in Japan and there was widespread opposition to restarts.
Premier Abe and utility companies have been pushing to get reactors back in operation, as the disaster forced Japan to turn to pricey fossil fuels to plug an energy gap left by the shutdown of dozens of nuclear reactors.
Abe has argued that resuming nuclear power was key to Japan's energy policy, but memories of Fukushima are still fresh for many.
Japan's entire stable of reactors was shuttered in the aftermath of the disaster, when a huge undersea quake sent a tsunami smashing into the coast, swamping the Fukushima Daiichi nuclear plant and sparking reactor meltdowns.
Official investigations have heaped blame on plant operator Tokyo Electric Power - three of its former executives are now facing a criminal trial - and the disaster has been labelled a "man-made" accident.
In response, Japan set up an independent atomic watchdog, the Nuclear Regulation Authority (NRA), replacing the previous arrangement where the industry ministry both oversaw the regulator and promoted nuclear power.