TOKYO - A 6.8-magnitude earthquake has hit Japan about 160 kilometres northeast of Tokyo.

The U.S. Geological Survey reports that the quake struck offshore at 1:45 a.m. Thursday.

National television and police say no injuries or damage have been reported so far in Tokyo, and no tsunami warning has been issued.

Japan is one of the world's most earthquake-prone countries because it sits atop four tectonic plates.