A small tsunami, less than half a metre high, struck parts of northern Japan Wednesday after a powerful earthquake shook the region.

The first wave made landfall on the eastern side of Hokkaido, Japan's large northern island, around 9:40 p.m. local time, more than an hour after an earthquake rocked the Kuril islands north of Japan.

Volcano Mendeleyev is silhouetted in this file photo against the sunset on Kunashiri Island, one of the Kuril islands, which stretch from the northern tip of Japan to Russia, an area included in Wednesday's tsunami warning.
(Associated Press)

A second wave measuring 20 centimetres hit the same area shortly after.

A tsunami warning was issued for the eastern coast of Hokkaido and stretches down the Pacific coast of the main island to Tokyo. Officials later included southern parts of Russia in the warning.

Officials had warned waves from the tsunami could be one to two metres high.

CBC

An official from the 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, which had a preliminary magnitude of 8.1. There were no immediate reports of damage or injuries, according to NHK.

The U.S. Geological Survey reported on its website that a 7.8-magnitude quake had been detected 440 kilometres east-northeast of the Kurils at a depth of 27.7 kilometres. It happened at 8:15 p.m. local time.

Tremors of magnitude 7.0 are generally classified as major earthquakes, capable of widespread, heavy damage.

Alaska, B.C. will be spared

Home to about 10,000 people, the Kuril islands stretch from the northern tip of Japan to Kamchatka, Russia. They separate the Sea of Okhotsk from the Pacific Ocean.

Russia and Japan both lay claim to the four southern islands in the thin chain, which are known in Japanese as the Chijima islands.

A tsunami warning was issued for the Alaska coastal areas from Dutch Harbor to Attu, while a tsunami watch is in effect from the northern tip of Vancouver Island to Alaska. Officials say the region likely won't experience any major effects. Hawaii is also under a tsunami advisory.

The quake was centred about 395 kilometres east of the island of Etorofu, in the Kurils about 1,600 kilometres northeast of Tokyo, the Japanese meteorological agency said.

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

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

With files from the Associated Press