A powerful earthquake has struck off the eastern coast of Japan, with officials warning that some regions could be hit by a small tsunami.

Japan's Meteorological Agency measured the 6.6-magnitude quake just before noon off Fukushima prefecture.

The agency issued a tsunami warning for Fukushima and Miyagi prefectures.

Reports said buildings shook in Tokyo with the force of the quake, but there was not thought to be any serious damage or any casualties.

Japan is one of the world's most earthquake-prone countries and experiences thousands of tremors each year.





