Earlier 5.0-magnitude and 6.7-magnitude earthquakes did not initially trigger a tsunami alert, but were followed by a 7.4-magnitude quake at 08.49am, prompting the USGS to warn that “hazardous tsunami waves are possible”.

It said the tsunami alert zone applied for coastal areas within a radius of 300km of the epicentre in the Pacific Ocean, off the city of Petropavlovsk-Kamchatsky.

The state of Alaska sits across the Bering Sea from the city, but no US territory appeared to be in the alert zone.

The initial earthquakes were followed by several aftershocks, including another 6.7-magnitude quake, said USGS.

The epicentre was around 140km east of Petropavlovsk-Kamchatsky, capital of the Kamchatka region.

The Kamchatka peninsula is the meeting point of the Pacific and North American tectonic plates, making it a seismic hot zone.

Since 1900, seven major earthquakes of magnitude 8.3 or higher have struck the area.