There were no immediate reports of damage or casualties from the tremor, which hit 85km off northwestern Honshu island.

A powerful earthquake has jolted northwestern Japan, prompting officials to issue a tsunami warning along the coast which was lifted two and a half hours later.

The quake, which had a magnitude of 6.4 according to the US Geological Survey (USGS), lasted for as long as 20 seconds and damage included a landslide that struck a road, public broadcaster NHK reported on Tuesday.

There were no initial reports of fatalities.

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Japan’s meteorological agency said it measured 6.7, and in some places was as high as a strong six on the agency’s seven-point “Shindo”, or Seismic Intensity Scale, which measures ground motion at specific points, unlike magnitude which expresses the amount of energy released.

Authorities lifted a 0.2-1.0-metre tsunami warning for the region after waves several centimetres high struck parts of the Niigata coast.

“We will work closely with local authorities to provide any disaster measures including lifesaving and rescue operations and have instructed officials to provide information in a timely and accurate manner,” Chief Cabinet Secretary Yoshihide Suga – the top government spokesman – told a media briefing.

Tokyo Electric Power Company’s (Tepco) Kashiwazaki-Kariwa nuclear plant was not affected by the quake, which hit 85km northeast of the site. All of its seven reactors were already shut down, NHK said.

A Tepco spokesman said an initial inspection showed no damage to the plant, and inspectors would carry out more detailed checks.

The quake also temporarily halted express bullet train services in the region, with some roads also closed, according to NHK.

Japan is on the so-called Pacific Ring of Fire where numerous devastating earthquakes have been recorded as well as volcanic eruptions.

On March 11, 2011, a magnitude 9.0 earthquake struck under the Pacific Ocean resulting in a tsunami that caused widespread damage and claimed thousands of lives.

That earthquake also sent three reactors into meltdown at the Fukushima nuclear plant, causing Japan’s worst post-World War II disaster and the most serious nuclear accident since Chernobyl in 1986.