Tsunami alerts have been issued across Japan after a magnitude 8 earthquake struck off Russia's east coast.

The quake, which was also picked up by the US Geological Survey, was shallow and strong enough to cause waves or a tsunami.

The Japan Weather Agency said it expected a tsunami of 1 metre (3.28 feet) to reach large coastal areas from around 2am UK time.

The US Tsunami Warning System also issued a warning of "hazardous tsunami waves" within the next three hours for some coasts of Russia and Japan, and put a tsunami watch in effect for Guam and US territories in the Pacific Ocean.

The earthquake off Kamchatka, a region in Russia's far east, has been called the "strongest in decades" by regional governor, who has urged people to move away from the coastline as Russia declares a tsunami threat.

Russia's regional governor also cited preliminary information to say no injuries had been caused by the earthquake, but a nursery had been damaged.

The small Russian town of Severo-Kurilsk in the Sakhalin region is being evacuated, according to the Sakhalin governor.