A huge earthquake measuring 8.0 on the Richter scale struck Japan's Hokkaido Island at 4:50 am (1950 GMT) and caused power blackouts on Hokkaido island, followed by a second quake measuring 7.8.

CNMI Emergency Management Office issued a tsunami alert 40 minutes later but Governor Juan Babauta lifted the warning after about three hours.

Measuring 5.0 on the Richter scale, the quake shook Miyagi prefecture, some 350 kilometers (220 miles) northeast of Tokyo, at 4:08 am (1908 GMT Sunday), an official from the Japan Meteorological Agency said.

The quake, the focus of which was ten kilometers (6.2 miles) deep, was located in northern Miyagi, and no tidal wave warning was issued after the tremor.

There were no immediate reports of injuries