The coastal areas were hit by a series of small waves that did not swell higher than 16 inches and rapidly diminished in size.

Japan's meteorological agency initially predicted that a 6 1/2-foot tsunami would hit the Pacific coast of its northernmost island of Hokkaido and main island of Honshu after 9:10 pm (7:10 am EST).

But a wave that hit the port of Nemuro on Hokkaido at 9:29 pm 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.

The quake struck at 6:15 am EST 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.

Russia's RIA-Novosti news agency reported that a tsunami warning was issued for the Kurils and Sakhalin, a large island that lies between the Kuril chain and Russia's eastern coast.

Southern Kurils residents were being evacuated from shoreline areas because of the tsunami threat, RIA-Novosti reported, citing emergency officials in the country's Far East. The Interfax agency reported that residents along the entire Kuril chain of more than 12 islands were being evacuated to safer areas.

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 Centre 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.