A 7.4-magnitude earthquake has struck off the coast of Kamchatka in Russia's Far East, the United States Geological Survey (USGS) said.

Saturday's quake hit 111 kilometres east of the Russian city of Petropavlovsk-Kamchatsky, the administrative centre of the Kamchatka region, at a depth of 39.5 kilometres, according to the USGS.

The Pacific Tsunami Warning Center said "hazardous" waves were possible along Russian coasts within 300 kilometres of the epicentre.

USGS earlier gave a magnitude of 7.5 before downgrading it.

In July, one of the strongest earthquakes ever recorded struck off the Kamchatka peninsula, triggering tsunamis up to four metres (12 feet) high across the Pacific and sparking evacuations from Hawaii to Japan.

The magnitude 8.8 quake was the largest since 2011, when a magnitude 9.1 tremor off Japan caused a tsunami that killed more than 15,000 people.

July's quake prompted authorities in Japan to order almost two million people to head to higher ground.

Tsunami warnings were also issued across the region, before being rescinded or downgraded.