The tremor had an epicentre in the Pacific Ocean and was 10km deep, according to the Japan Meteorological Agency. The biggest waves were expected in Iwate, Aomori and Hokkaido prefectures, authorities said.

Speaking to reporters, prime minister Sanae Takaichi said the government had set up an emergency task force and urged citizens in the affected areas to evacuate to safety.

Broadcaster NHK showed ships sailing out of Hachinohe port in Hokkaido in anticipation of the waves, as an alert ‘Tsunami! Evacuate!’ flashed across the screen.

Bullet train services in Aomori at the northern tip of Japan’s main Honshu island were halted due to the tremors, Kyodo news agency reported.

The quake measured an ‘upper 5’ on Japan’s seismic intensity scale — strong enough to make it difficult for people to move around. In many cases, unreinforced concrete-block walls collapse.

Japan is one of the world’s most earthquake-prone countries, with a tremor occurring at least every five minutes. Located in the “Ring of Fire” of volcanoes and oceanic trenches partly encircling the Pacific Basin, Japan accounts for about 20% of the world’s earthquakes of magnitude 6.0 or more.

There are no nuclear power plants currently in operation in Hokkaido and Tohoku regions but Hokkaido Electric Power and Tohoku Electric Power Co have a number of shutdown nuclear power plants there. Tohoku Electric said it was checking the impact of the earthquake and tsunami on its Onagawa nuclear power plant.