One person was killed and at least seven were missing on Saturday, officials said, as "unprecedented" rains triggered floods and landslides in Japan's quake-hit region of Ishikawa, where authorities told tens of thousands to evacuate.

A dozen rivers in the region, on the west coast of central Japan that was hit by a large quake on New Year's Day, had burst their banks by 11:00 am (0200 GMT), land ministry official Masaru Kojima said.

One person was killed, three people were missing and two people were seriously injured in Ishikawa, the region's government said in a statement, with two of the missing reportedly carried away by strong river currents.

Another four people, who were working for the land ministry to restore a road in Wajima, were also missing, ministry official Koji Yamamoto told AFP.

"About 60 people have been working to restore a road hit by the quake but a landslide occurred" on Saturday morning, Yamamoto said.

"I asked (contractors) to check the safety of workers... but we are still unable to contact four people," he said.

Rescue workers were on their way to the site but were "blocked by landslides".

About 20 workers were taking shelter inside a tunnel they had been working to restore, Yamamoto said.

Japan's Kyodo news agency said as many as 10 people were missing in Wajima.

Many buildings were inundated, with landslides blocking roads, some 6,000 households without power and an unknown number of households without running water, the Ishikawa government said.

Communication services were also cut for some people, operators said.

The cities of Wajima and Suzu, as well as Noto town, ordered about 44,700 residents to evacuate, officials said.

Another 16,700 residents in Niigata and Yamagata prefectures north of Ishikawa were also told to evacuate, the fire and disaster management agency said.

'Life-threatening situation'

The Japan Meteorological Agency (JMA) said it issued its highest-level warning for Ishikawa, advising of a "life-threatening situation".

The areas under the warning were seeing "heavy rain of unprecedented levels", JMA forecaster Satoshi Sugimoto told reporters, adding "it is a situation in which you have to secure your safety immediately".

More than 120 millimetres (4.7 inches) of rainfall per hour was recorded in Wajima in the morning, the heaviest rain since comparative data became available in 1929.

Footage on NHK showed an entire street submerged in Wajima.

Prime Minister Fumio Kishida instructed the government "to do its best in disaster management with saving people's lives as the first priority", top government spokesman Yoshimasa Hayashi told reporters.

Self-Defense Force personnel have been sent to the Ishikawa region to join rescue workers, he said.

Wajima and Suzu, in central Japan's Noto peninsula, were among the areas hardest hit by the huge New Year's Day earthquake that killed at least 236 people.

The region is still reeling from the magnitude 7.5 quake that toppled buildings, ripped up roads and sparked a major fire.

Parts of Japan have seen unprecedented rainfall in recent years, with floods and landslides sometimes causing casualties.

Scientists say human-driven climate change is intensifying the risk of heavy rain in the country and elsewhere because a warmer atmosphere holds more water.