TOKYO (REUTERS) - The Japan Meteorological Agency issued a "yellow" warning early on Saturday morning that a small tsunami would reach the Japanese coast at Fukushima, site of a wrecked nuclear power plant, at 1740 GMT (1.40am).

There were no immediate reports of damage on land from the quake, classified as magnitude 6.8 by the Japanese authorities, which struck some 370km off Japan's eastern coast.

A yellow warning is issued when a tsunami is not expected to exceed a height of 1m, far smaller than the wave that hit the plant in 2011.