A Japanese utility on Monday said that a surprise glitch has switched off a nuclear reactor just days after it was turned on again after a nationwide shutdown following the 2011 Fukushima crisis.

Kansai Electric Power had been planning to start generating electricity on Monday from its No. 4 reactor at the Takahama plant, 380 kilometres (236 miles) west of Tokyo.

But the reactor unexpectedly shut down Monday afternoon after the restart began Friday, marking the first major technical problem for a restart since Tokyo approved switching on sites considered safe.

Operator Osaka-based Kansai Electric said it was probing the cause.

The reactor had been the fourth to come back online after the 2011 Fukushima disaster, the worst nuclear crisis in a generation.

Last month, Kansai Electric switched on another reactor at the Takahama plant, despite stiff opposition from local residents.

The region's Fukui District Court in December overturned an injunction preventing a restart of the two reactors which had been won by residents. They had argued it was not proven to be safe despite a green light from the national Nuclear Regulation Authority.

Two reactors in the southern prefecture of Kagoshima, operated by Kyushu Electric Power, restarted in August and October of last year, ending the two-year hiatus in nuclear power generation.

A pair 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.

Prime Minister Shinzo Abe and utility companies have been pushing to get reactors back in operation nearly five years after a huge earthquake and tsunami caused a disastrous meltdown at the Fukushima power plant.

The accident forced resource-poor 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.

oh/pb/eb

THE KANSAI ELECTRIC POWER CO