A magnitude 7.4 earthquake struck off Japan's Sanriku coast on April 20, registering an upper 5 reading on the Japanese seismic intensity scale in Hashikami, Aomori Prefecture, the Asahi Shimbun reported.

NHK television, Japan's state broadcaster is currently reporting that tsunami waves have begun to hit the coast and are reporting several warning of people to seek higher ground. 

Waves of 40cm have already been reported on the eastern coast of Japan, with larger waves following. 

Japan's Meteorological Agency said the quake hit at 16:53 local time at a depth of around 10km. Tsunami warnings and advisories were issued for the Pacific coastlines of Hokkaido and the Tohoku region.

The agency also issued an emergency earthquake early warning before the strongest shaking arrived.

Lower 5 intensity readings were registered in the Aomori cities and towns of Hachinohe, Shichinohe, Tohoku, Oirase, Gonohe and Nanbu. In Iwate Prefecture, the same intensity was recorded in Miyako, Fudai, Morioka, Ninohe, Hachimantai, Yahaba and Hanamaki. In Miyagi Prefecture, lower 5 readings were reported in Tome and Wakuya.

Shindo 4 readings were recorded across a wide area of Aomori, Iwate and Miyagi prefectures, as well as in Hakodate in Hokkaido and Niikappu, plus parts of Akita, Yamagata and Fukushima prefectures.

The Sanriku coast, which faces the Pacific Ocean off Japan's northeastern coast, was the area worst affected by the March 2011 Great East Japan Earthquake and tsunami that killed more than 18,000 people and triggered the Fukushima Daiichi nuclear disaster.