An earthquake measuring 6.8 on the Richter scale struck northern Japan Wednesday evening and a tsunami warning has been issued.

The quake's epicenter was about 235 kilometers (146 miles) south of Kushiro, Hokkaido, and 734 kilometers (456 miles) northeast of Tokyo, the Japan Meteorological Agency said.

The quake, which occurred at 6:08:37 pm local time, was 26.6 kilometers (16.5 miles) deep, the USGS said.

A tsunami warning for a wave with an estimated height of 50 cm has been issued by the Meteorological Agency. The tsunami waves were expected to reach the coasts of Aomori and Iwate prefectures at 6:40 pm (0940 GMT).

No injuries or damage were reported.