The operator of a Japanese nuclear plant whose restart was blocked this week by a court injunction said Friday it would appeal the ruling.

Kansai Electric Power (KEPCO) has submitted "a motion of complaint to Fukui district court" over Tuesday's injunction banning the re-firing of reactors No.3 and 4 at the Takahama nuclear plant in central Japan, a company spokesman told AFP.

In its ruling, the court said the safety of the reactors at Takahama had not been proved, despite a green light from industry watchdog the Nuclear Regulation Authority (NRA), whose guidelines, the court said, were "too loose" and "lacking in rationality".

"We genuinely regret that the court did not understand our argument," the spokesman said, adding the temporary court order "includes significant factual errors".

The nuclear issue is a highly sensitive one in Japan, which remains deeply scarred by the tsunami-sparked disaster at Fukushima in 2011, when reactors went into meltdown after their cooling systems were flooded.

The worst atomic accident in a generation forced tens of thousands of people from their homes, with some still displaced and scientists warning tracts of land might be uninhabitable for decades.

Japan's entire stable of reactors -- which once provided a quarter of the country's electricity -- was gradually switched off following the disaster.

Activists are also seeking an injunction to prevent the restart of reactors at the Sendai plant in southern Japan, with the court expected to rule on April 22.

But pro-atomic Prime Minister Shinzo Abe has backed an industry push to return to nuclear, with the country's Japan's manufacturers complaining over the high cost of electricity produced from dollar-denominated fossil fuels.