A tsunami is expected to hit northern Japan and Russia's Pacific coast, the US Pacific Tsunami Warning Center says.
Japanese meteorologists say a tsunami of at least two metres (6.5 feet) high could hit Hokkaido and Honshu islands after 2110 (1210 GMT).
Warnings are being broadcast on all Japanese TV and radio stations advising people to move to higher ground.
It comes after an earthquake of at least 8.1 magnitude hit the Kuril Islands, north of Japan.
The earthquake struck about 390km (240 miles) east of Iturup, known as Etorofu in Japan, at 1115 GMT, the meteorological agency said.
Other smaller waves may batter the Pacific coast of Japan over the next hour, the agency said.
http://news.bbc.co.uk/1/hi/world/asia-pacific/6150538.stm
