A strong 5.9-magnitude earthquake struck early Thursday off the eastern coast of Japan, the US Geological Survey said, but no tsunami warning was issued.
The epicentre of the quake, which struck at a depth of 25.4 kilometres (16 miles), was located offshore about 41 kilometres southeast of Hasaki in Chiba prefecture, east of Tokyo.
The Japan Meteorological Agency, which put the magnitude at 6.2, said on its website that the quake "poses no tsunami risk".
The tremor, which struck at 4:47 am (1947 GMT Wednesday), was felt in the greater Tokyo area, local media reported.
Japan sits on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches through Southeast Asia and across the Pacific basin.
In 2011, a devastating 9.0-magnitude earthquake struck off Miyagi prefecture, unleashing an enormous tsunami, triggering the Fukushima nuclear reactor meltdown and killing nearly 16,000 people. More than 2,500 others are still missing.