A powerful 7.7 magnitude earthquake struck in the Sea of Okhotsk off the east Russian coast early Tuesday, US monitors said, but no tsunami warning was immediately issued.

The quake occurred at 0259 GMT some 158 kilometres (100 miles) east-north-east of Poronaysk, Russia, at a comparatively deep 625 kilometres (390 miles) down, the US Geological Survey said in an initial report.

The Pacific Tsunami Warning Centre said in a first and final bulletin that based on all available data a destructive tsunami was not expected.

* 7.3 magnitude tremor jolts sea off Japan's Hokkaido

A magnitude 7.3 earthquake jolted Japan's southern sea of Okhotsk at 12:01 JST (0258 GMT) on Tuesday, according to Japan Meteorological Agency (JMA).

The epicenter was located 49.3 north latitude, 145.7 east longitude with a depth of 590 km, said JMA.

No tsunami alert has been issued and no damage has been reported so far.

VNN/Xinhua/AFP