A Japanese utility on Thursday lodged an appeal against a ban on restarting two nuclear reactors, after a court came down on the side of campaigners for the first time since the Fukushima disaster.

The appeal came after Fukui District Court said Wednesday two reactors at its Oi plant should not be restarted because they pose "specific risks" to residents in the event of a major earthquake.

"It was extremely regrettable that our company's position could not be understood," Kansai Electric Power said in a statement.

"During an appeal, our company will continue to stress the safety of the number three and number four reactors at the Oi plant," the company said.

The ruling was the first against the restarting of reactors since a massive earthquake and tsunami sparked meltdowns at the Fukushima nuclear plant in March 2011, and was a blow to government plans to bring some back online.

At present, all of Japan's nearly 50 nuclear reactors are offline due to shutdowns or safety checks.

The court was responding to a lawsuit filed by a group of 189 people demanding an injunction against the restarting of the reactors. It acknowledged claims by 166 of them who live within 250 kilometres (156 miles) of the plant.

In the face of widespread public unease about nuclear power, the Nuclear Regulation Authority in July last year introduced new safety standards. These oblige plant operators to put in place specific countermeasures against serious accidents like meltdowns or tsunamis.

Despite the ruling, the government of Prime Minister Shinzo Abe said there was no change in its plan to restart nuclear reactors if they are confirmed safe.

"As a country, we are going to explain to local people about reactors that are found to be safe after thorough checking," Chief Cabinet Secretary Yoshihide Suga told a news conference after the firm appealed the ruling.

"This basic stance has not changed at all," the top government spokesman said.

Japan shut down all its nuclear reactors after Fukushima. The two reactors at Fukui resumed operations in August 2012, the first and only ones to do so.

In September last year they were stopped for regular safety checks.