A series of small tsunami waves have hit Japan's northernmost island after a major quake in the Kurile islands triggered a full-scale tsunami warning for areas of northern Japan and Russia's Pacific coast.
Japanese media reported that a wave measuring about 40 cm had come ashore at Nemuro, on the east coast of Japan's Hokkaido island.
NHK public television in Japan said local authorities in Hokkaido had been bracing for a tsunami predicted at between 1 to 2 metres in height.
A lesser warning was issued for a wide swathe of the eastern coast of northern and central Honshu, Japan's main island, but for waves expected to be some 50 cm at highest.
A tsunami warning was also issued to all coastal areas in the Kuriles, NHK public television quoted Itar-Tass news agency as saying.
Both the Pacific Tsunami Warning Center in Hawaii and Japan's Meteorological Agency put the quake's intensity at 8.1. Its epicentre was deep under the Pacific Ocean roughly 1,700 km northeast of Tokyo.
The US Geological Survey said the quake occurred at 8.14pm (11.14am Irish time) with the focus 27.7km below the seabed.
Hokkaido residents reported feeling little to no shaking from the earthquake, but authorities stopped trains in the eastern part of the island and warned people to move to higher ground.
"We have been repeatedly urging people to evacuate. We did not feel an earthquake," said Yasukatsu Imai, an official in the Nemuro local government, told NHK.
Authorities in Russia's Sakhalin region said the earthquake had struck near uninhabited islands at the centre of the Kuriles chain. The Russian Emergencies Ministry said a tsunami had yet to be spotted.
Russia's Shell-led Sakhalin-2 oil and gas exploration project said that there had been no immediate impact on their activities from the earthquake and tsunami.
The Kuriles are known as the Chishima islands in Japan.
Japan claims the four islands closest to Hokkaido, calling them the Northern Territories. The Soviet Union seized the islands, which it knows as the Southern Kuriles, at the end of World War Two and Tokyo and Moscow continue to wrangle about their future.