A powerful earthquake of magnitude 7.8 struck Russia's Kamchatka Peninsula on Tuesday, the US Geological Survey and US Pacific Tsumani Centre said.

The quake struck at 11:34 am, some 125 miles (200 km) from the city of Nikolskoye on Bering Island off the Kamchatka Peninsula, according to Reuters.

The epicentre was west of Attu, the westernmost and largest island in the Near Islands group of Alaska's remote Aleutian Islands.

The US Pacific Tsunami Warning Center had warned earlier that "hazardous tsunami waves were possible for coasts within 300 km (186 miles) of the earthquake epicentre." But it later said that based on all available data the tsunami threat from this earthquake had passed.

The quake was initially reported as a magnitude 7.7 before being revised down to 7.4 and finally upgraded to 7.8, a major quake normally capable of causing widespread and heavy damage when striking on or near land.

The quake was followed by numerous aftershocks, including several above magnitude 5.0.