Japan's Meteorological Agency has forecast tsunami waves of up to 3m for Pacific coastal areas of central Hokkaido, Aomori and Iwate prefectures following a magnitude 7.4 earthquake off the Sanriku coast on April 20, the Asahi Shimbun reported.

State NHK, citing the Meteorological Agency, said that waves have already begun to hit, with the tsunami wave currently at 70cm, with its peak estimated at 3 metres in the next few minutes in several locations along Japan's eastern coast. 

Fuji Port has reported 70cm waves have already begun to come ashore, with live video monitoring occuring across the country. 

A tsunami warning is in effect for the central Pacific coast of Hokkaido, with the first wave forecast to arrive at 17:30 local time and a maximum wave height of 3m.

The Aomori Pacific coast warning is also at 3m, with the first wave estimated to be arriving. The first wave has been confirmed in Iwate, also at the 3m threshold.

A lower-level tsunami advisory has been issued for the eastern and western Pacific coasts of Hokkaido, the Sea of Japan coast of Aomori and the coastlines of Miyagi and Fukushima, with maximum wave heights of 1m forecast.

The first observed wave reached Miyako in Iwate Prefecture at 17:10, with a maximum wave height of 0.4m recorded at 17:21.

The earthquake struck at 16:53 local time at a depth of around 10km off the Sanriku coast. The maximum recorded seismic intensity was upper 5 on Japan's seven-point shindo scale, registered in Hashikami, Aomori Prefecture.

The Sanriku coast was the area most severely 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.

The agency has urged residents in warning areas to evacuate to higher ground immediately.