A magnitude 7.7 earthquake that hit waters off Russia's Pacific island of Sakhalin today inflicted no casualties or damage, Russian officials said.

The Russian Emergency Situations Ministry's branch on Sakhalin said the quake was centered in the Sea of Okhotsk about 160 kilometres east of Poronaysk, Russia, at a depth of more than 600 kilometres.

The US Geological Survey said the quake, which struck at 1 pm local time today, had a magnitude of 7.7, while the Russian ministry put it at 6.3.

"There have been no victims or damage," the ministry said in a statement, adding that the quake was felt as magnitude 2 to 3 shocks in towns and villages on Sakhalin. The ministry said that there was no danger of tsunami and that aftershocks were unlikely.

In Japan, the Meteorological Agency also reported that there was no risk of a tsunami from the quake. Its readings showed the quake was mildly felt on the northern Japanese island of Hokkaido and in the northeastern section of Honshu, Japan's main island.