11 nuclear power plants have been shut down in Japan after an 8.9 magnitude earthquake hit the country, causing a major blackout.

Tokyo Electric Power Company said in a statement that 4 million households are in power outage and some units at its Fukushima Daiichi and Fukushima Daini nuclear facilities have been automatically stopped.

The earthquake, which hit the northern part of the country at 3:15pm (06.15 GMT), triggered a 10m tsunami that swept away everything in its path, including houses and cars, local reporters said.

Japan’s Tohoku Electric Power Company said power was cut to all of its customers in three prefectures – Aomori, Iwate and Akita after the quake, which is believed to have killed at least 20 people.

Power was also cut off in almost all areas of Miyagi and Yamagata prefectures and in some areas in Fukushima and Niigata prefectures, reports Reuters.

Tsunami warnings have been issued to Hawaii, Australia, New Zealand, the entire US west coast, Mexico, Central and South America.

Coastal areas are now being evacuated in the US state of Hawaii, where waves are due to hit at 3am local time (13.00 GMT).