The US Geological Survey said the quake occurred at 0325 GMT at a depth of 160 kilometres (100 miles), about 95 kilometres northeast of the Russian town of Yelizovo in the mountainous Kamchatka Krai region. It put the magnitude at 7.0.
The Russian Academy of Sciences said on its website the first tremor, which it said measured 7.3 in magnitude, was followed minutes later by a 5.2 magnitude aftershock.
Residents of regional capital Petropavlovsk-Kamchatsky felt the earth tremble, a spokesman for the local branch of the Academy told Russia's Interfax news agency. The quake struck in an area close to the "Ring of Fire", an arc of fault lines that circle the Pacific Ocean which is prone to frequent earthquakes and volcanic eruptions. The National and Pacific Tsunami Warning Centers said there was no risk the earthquake had caused a tsunami.