Tokyo: A strong 6.8-magnitude earthquake struck off the coast of northeastern Japan this morning, the US Geological Survey said, but authorities did not issue a tsunami warning and there were no immediate reports of damage.

The quake struck at 6:12 am (local time) off the east coast of Japan's Honshu island in the Pacific Ocean, according to USGS, at a depth of 38.9 kilometres.

Japan's meteorological agency said there was no immediate tsunami threat from the quake.

The quake hit 33 kilometres south east of the nearest city of Ofunato.

Japan's islands are situated at the conjuncture of several tectonic plates and experience a number of relatively violent quakes every year.