WASHINGTON (AFP) - A powerful 7.7 magnitude earthquake struck in the Sea of Okhotsk off the east Russian coast early Tuesday, US and Japanese monitors said, with the tremor felt as far away as Tokyo. The quake occurred at 0259 GMT some 158 kilometers (100 miles) east of Poronaysk, Russia, with the epicenter a comparatively deep 625 kilometers (390 miles) down, the US Geological Survey said in an initial report. Japan’s Meteorological agency said the tremor was felt throughout the country’s northern island of Hokkaido, but the Pacific Tsunami Warning Center said in a first and final bulletin that a destructive tsunami was not expected.