An 8.8 magnitude megaquake struck off the coast of Russia's far eastern Kamchatka peninsula earlier, prompting evacuations and tsunami alerts across parts of the Pacific coast.

In Severo-Kurilsk, a Russian town of about 2,000 people some 350 kilometres (217 miles) southwest of the earthquake's epicentre, tsunami waves crashed through the port area and submerged the local fishing plant, according to authorities.

The town lies on the northern Kuril island of Paramushir, just south of the Kamchatka peninsula.

The waves, which were up to four metres high in some areas, reached as far as the town's World War II monument about 400 metres (1,312 feet) from the shoreline, according to Mayor Alexander Ovsyannikov.

Most of the town lies on higher ground safe from flooding, he added.

"Everyone was evacuated. There was enough time, a whole hour. So everyone was evacuated, all the people are in the tsunami safety zone," he said at a crisis meeting with officials earlier.

- 'Everyone acted quickly' -

The Kremlin said "all warning systems" had worked properly.

"Thank God, there were no casualties," spokesman Dmitry Peskov told reporters including AFP.

An expedition group from the Russian Geographical Society was on the neighbouring island of Shumshu when the tsunami swept away their tent camp.

"When the wave hit, all we could do was run to higher ground. It's very difficult to do that in boots on slippery grass and in fog," group member Vera Kostamo told Russian tabloid Komsomolskaya Pravda.

"All the tents and structures were swept away by the wave, and our belongings were scattered across the beach for hundreds of metres," she added.

"We have no casualties, everyone acted quickly, but we lost all our belongings."

Authorities in the Sakhalin region, which includes the northern Kuril Islands, declared a state of emergency.

The regional seismic monitoring service said the earthquake was the region's strongest since 1952.

"Strong aftershocks with a magnitude of up to 7.5 should be expected," it added.