TOKYO, April 21. /TASS/. At least six people were injured as a result of a powerful, magnitude 7.7, earthquake that struck the east of Japan’s northeastern coast on Monday, Japanese Disaster Management Minister Jiro Akama said.

Four of the injured sustained minor injuries, while two were seriously hurt, the Kyodo news agency reported, citing the minister.

The earthquake occurred in the Pacific Ocean, east of the coast of the northeastern Tohoku Region. A tsunami warning of waves up to three meters high was then issued for the coasts of the northeastern prefectures of Iwate, Aomori, and Miyagi, as well as the southern part of Hokkaido. Waves of up to 80 centimeters reached the shore.

Nine aftershocks with magnitudes of up to 5.4 followed the earthquake, according to TASS calculations based on data from the Japan Meteorological Agency. Seismologists warned that the risk of similar tremors will persist for about a week.