A strong earthquake with a magnitude of 7.7 hit the Sea of Okhotsk, off Russia's eastern Pacific coast, early Tuesday, but no casualties were reported, the U.S. Geological Survey said.

The epicenter was a deep 625 km down in the waters off Russia's Sakhalin Island to the north of Japan and the quake struck at 1 p.m. local time, USGS said in an initial report.

"There have been no victims or damage," the Russian ministry said in a statement, adding that the quake was felt as magnitude 2 to 3 shocks in towns and villages on Sakhalin, AP report said.

The earthquake's jolt was also felt in Tokyo. The Japanese meteorological agency reported that mild tremors were felt throughout the northern island of Hokkaido and in the northeastern section of Honshu, but there is no danger of tsunami or aftershocks, as reported by AP.