The waves did not swell higher than 16 inches and rapidly diminished in size, but Japan's meteorological agency said that it would wait for at least several hours before withdrawing its warning of possible larger waves.

Initial reports are the 8.1 magnitude earthquake hit 6.7 miles north of the Kuril Islands and led the Pacific Tsunami Warning Center to issue a tsunami watch here in Hawai'i, with an estimated time of arrival for any tsunami to hit Hawai'i at 7:20 a.m.

Ray Lovell, spokesman for State Civil Defense, said the state is monitoring the watch and if it elevates to a warning, the Emergency Alert System will be initiated and sirens will sound to alert residents and visitors to immediately get away from the shorelines and get to higher ground.

Meanwhile, Japan's meteorological agency told coast residents to flee to higher ground after initially predicting that a 6-foot tsunami would hit the Pacific coast of its northernmost island of Hokkaido and main island of Honshu after 2:10 a.m., HST.

A wave that hit the port of Nemuro on Hokkaido at 2:29 a.m. was measured at 16 inches, and live footage from the area showed calm seas. A few minutes later, a second, 8-inch wave hit the nearby port city of Kushiro, the agency said, and the waves got progressively smaller.

A magnitude 9.1-magnitude earthquake off the coast of Indonesia on Dec. 26, 2004 caused tsunami as high as 33 feet that killed at least 213,000 people in 11 countries.

Takeshi Hachimine, chief of the Japanese meteorological agency's earthquake and tsunami monitoring section, said aftershocks of Wednesday's quake could trigger more tsunami — but those waves are expected to pose little danger to Japan.

The quake struck at 1:15 a.m. HST with a preliminary magnitude of 8.1 about 245 miles east of the island known in Japan as Etorofu, which is about 110 miles northeast of Hokkaido, according to the Japanese meteorological agency.

Etorofu is one of four islands claimed by both Japan and Russia. The disputed islands are known in Russia as the Southern Kurils and in Japan as the Northern Territories. Etorofu is known in Russia as Iturup.

A tsunami warning was issued for the Kurils and Sakhalin, a large island that lies between the Kuril chain and Russia's eastern coast, but was later lifted.

Residents in the sparsely poulated Kurils were warned of the threat but were not evacuated and no damage or casualties were reported in Russia as a result of the quake, said Olga Shekhovtseva, chief spokewoman for the Emergency Situations Ministry branch in the Sakhalin region, which includes the Kuril Islands.

The islands have rich natural resources but their population has plummeted to just 9,900, according to official statistics.

The ITAR-Tass agency reported that Russia's Pacific Fleet ships took refuge at their bases but were ready to help with rescue operations if necessary.

A tsunami warning was in effect on the coastal areas of Alaska, and the Alaska Tsunami Warning Center advised people in low-lying coastal areas to be alert to instructions from local officials. It said people on beaches in the warning area should move to higher ground.

A watch was in effect for the northern tip of British Columbia, and precautionary advisories were issued for coastal areas in Washington, Oregon and California.

An official from the Japanese town of Shibetsu on Hokkaido, Kiyoshi Takimoto, told public broadcaster NHK that about 4,000 of the town's 6,100 residents lived along the coast and had been told to flee to higher ground.

Takimoto said he didn't notice the quake. There were no immediate reports of damage or injuries, according to NHK.

In the city of Kushiro, fire department and city officials urged residents to move to safety, city official Masatoshi Sato said. Railway officials ordered local trains on Hokkaido to stop at nearby stations as a precautionary step, NHK said.

The U.S. Geological Survey reported on its Web site that a 7.8-magnitude quake had been detected 275 miles east-northeast of the Kurils at a depth of 17.2 miles. Temblors of magnitude 7 are generally classified as major earthquakes, capable of widespread, heavy damage.

Tsunami waves, which are generated by earthquakes, are often barely noticeable in the ocean but can rise to great heights once they arrive at shore.

Japan is one of the world's most earthquake-prone countries because it sits atop four tectonic plates.