Japan's meteorological agency has issued a tsunami warning for the country's Pacific Coast, according to reports.
The warning said the wave is expected to measure at least 2m (6.5 feet) tall and to hit the country's north and east coasts at 12.10 GMT, 9.10pm local time. Residents were told to flee to higher ground.
The alert, which was carried on Japanese state television, was issued after an earthquake with preliminary magnitude 8.1 hit the Russian-administered Kuril islands north of Japan at 11.15 GMT this morning.
"This is an emergency warning about tsunami tidal waves," the warning said. "If you are by the coast and felt tremors, you must evacuate immediately to higher ground."
A tsunami has been forecast to hit the Pacific coast of Japanís northernmost island of Hokkaido and main island of Honshu after noon, the agency said. The largest waves were expected to hit Hokkaido, with smaller waves striking further south.
An official from Shibetsu on Hokkaido, Kiyoshi Takimoto, told public broadcaster NHK that about 4,000 of the townís 6,100 residents lived along the coast and had been told to flee to higher ground. Mr Takimoto said he didnít notice the quake.
In the city of Kushiro, fire department and city officials were urging residents to move to safety, city official Masatoshi Sato told AP. Keiichi Kimura, a Hokkaido Prefectural (state) police officer, said there were no immediate reports of injuries or damage from the quake. Railway officials ordered local trains on Hokkaido to stop at nearby stations as a precautionary step, NHK reported.
The US Geological Survey initially reported that the earthquake had a magnitude of 7.8 on the Richter scale and took place 27.7km underground.
That was revised to 8.1 as the body's Pacific Tsunami Warning Centre issued an alert to Russia, Japan, and the Pacific Marcus, Wade and Midway islands.
A tsunami watch, a lower level warning, was issued to Hawaii, Taiwan, the Philippines, Indonesia, Nauru and Papua New Guinea as well as several island clusters across the Pacific.
The centre said the earthquake was of sufficient magnitude to generate a tsunami but that was no guarantee that a wave would be formed.
"It is not known that a tsunami was generated," it said in a bulletin. "This warning is based only on the earthquake evaluation. An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicentre within minutes to hours."
"Authorities in the region should take appropriate action in response to this possibility."
Tsunamis are triggered by particular movements of the ocean floor during an earthquake. The sea bed must rise and fall, displacing water, to generate significant tsunamis. Earthquakes of great magnitude, in which the tectonic plates rub against each other but do not cause much vertical movement, can take place without creating waves.
The Indian Ocean tsunami, which nearly two years ago, on Boxing Day, 2004, followed an earthquake measuring 9.15 on the Richter scale off the coast of Indonesia. The waves devastated coastlines across south Asia, leaving 230,000 people dead or missing.