At least six people have been injured after a powerful 7.7-magnitude earthquake struck northeastern Japan on April 20, Emergency Situations Minister Jiro Akama said.
Four of the injured suffered minor injuries and two were seriously injured, Kyodo news agency reported, citing the minister.
The earthquake struck in the Pacific Ocean, east of the coast of the northeastern Tohoku region. A tsunami warning of up to three meters was issued for the coasts of northeastern Iwate, Aomori and Miyagi prefectures, as well as southern Hokkaido. Waves up to 80 cm high have reached the coast.
The earthquake was followed by nine aftershocks, each with a magnitude of up to 5.4. Seismologists warn that the risk of tremors similar to the one on April 20 will persist for a week.