A powerful and shallow 7.5-magnitude earthquake struck off Japan's northeast coast, triggering a tsunami at Kuji Port in Iwate Prefecture.

Public broadcaster NHK initially warned that a tsunami up to 10 feet high was expected to hit the Iwate area on Honshu's main island. However, so far, it has been reported to be about 31 inches high.

The quake was reported shortly before 17:00 local time, rattled towers as far away as Tokyo, and forced the suspension of Shinkansen high-speed rail services in Iwate, NHK said.

Prime Minister Sanae Takaichi said the government had mobilized an emergency task force and urged citizens in affected areas to evacuate.

"Possible damage and casualties are now being looked into," Takaichi told reporters in Tokyo.

Japan sits on the Pacific "Ring of Fire," one of the world's most seismically active zones, where multiple tectonic plates collide and generate earthquakes.

Since the 2011 Fukushima disaster, when a 9.0-magnitude quake and tsunami sparked triple reactor meltdowns, Japan has overhauled its response and evacuation systems to improve disaster readiness.

NHK cited the Tokyo Electric Power Company as saying that no issues were reported at the Fukushima Daiichi and Fukushima Daini nuclear power plants.

The Japan Meteorological Agency warned that aftershocks are possible over the next week and could be similar in size to the quake recorded earlier today.