Japan lowers tsunami warning but tells people not to return home ...

Japan dropped its highest-level tsunami alert, issued following a series of major earthquakes on Monday, but told residents of coastal areas not to return to their homes as deadly waves could still come.

The quakes, the largest of which had a magnitude of 7.6, started a fire and collapsed buildings on the west coast of Japan's main island, Honshu.

One elderly man was pronounced dead after a building collapsed in the town of Shika in Ishikawa Prefecture, broadcaster NTV reported, citing local police.

The Japan Meterological Agency said more than a dozen quakes struck in the Japan Sea off the coast of Ishikawa and nearby prefectures shortly after 4 p.m. local time.

The agency initially issued a major tsunami warning for Ishikawa and lower-level tsunami warnings or advisories for the rest of the western coast of Honshu, as well as the northernmost of its main islands, Hokkaido. 

The warning was downgraded to a regular tsunami several hours later, meaning the waters could still reach up to three metres. Aftershocks could also slam the same area over the next few days, it said. 

Government spokesperson Yoshimasa Hayashi told reporters that nuclear plants in the area had not reported any irregularities, but said it was critical for people in coastal areas to get away from the oncoming tsunami.

"Every minute counts. Please evacuate to a safe area immediately," he said.

The government said that as of Monday night it had ordered more than 97,000 people in nine prefectures on the coast to evacuate.

People returning to get their wallets and other belongings have been known to be swept away and drowned even hours after the first evacuation warning. People were evacuated to stadiums, where they will likely have to stay for a few days.

The earthquakes themselves also caused damage. Japanese news footage showed smoke and flames spewing from an area in Wajima city, Ishikawa Prefecture, where there reports of at least 30 collapsed buildings. Images carried by local media showed a building collapsing in a plume of dust in the coastal city of Suzu. 

The quake also jolted buildings in the capital Tokyo, some 500 kilometres from Wajima on the opposite coast.

More than 36,000 households had lost power in Ishikawa and Toyama prefectures, utilities provider Hokuriku Electric Power said. Bullet trains in those areas were halted.

Japanese media reports showed a crowd of people, including a woman with a baby on her back, standing by huge cracks that had ripped through the pavement in Wajima.

The Meteorological Agency said in a nationally broadcast news conference that more major quakes could hit the area over the next week, especially in the next two or three days.

Tsunami warnings were also issued for Japan's northernmost main island of Hokkaido and parts of North Korea and Russia. Russian officials issued a tsunami alert for the island of Sakhalin, warning areas across the island's west coast could be affected by the waves.

In South Korea, the country's weather agency urged residents in some eastern coastal towns to watch for possible changes in sea levels. The first tsunami to reach South Korea's coast was 67 centimetres (2.2 feet) but it may increase in size after the initial waves and may continue for more than 24 hours, the agency said.

South Korea's Gangwon province warned people to take precautions and evacuate to higher ground.

Separately, North Korea issued tsunami warnings for its coast of possible waves of more than two metres, South Korea's Yonhap news agency reported, citing the North's state radio.

The Japanese government has set up a special emergency centre to gather information on the quakes and tsunami and relay them speedily to residents to ensure safety, Prime Minister Fumio Kishida told reporters.

He reiterated the warning for immediate evacuation in affected areas.

Japan is an extremely quake-prone nation. In March 2011, a major quake and tsunami caused meltdowns at a nuclear plant.