A powerful 7.5-magnitude earthquake shook northeastern Japan late on Monday, injuring more than 20 people and triggering tsunami warnings that, hours later, were downgraded to advisories.

The entire northern coast of Japan is today under a tsunami alert after a 7.6 magnitude earthquake struck.

Japan's Prime Minister Sanae Takaichi said during a press briefing in Tokyo that at least 30 people were injured, one seriously.