An earthquake with a preliminary magnitude of 5.9 jolted northeastern Japan on Saturday, but no tsunami warning was issued, the Japan Meteorological Agency said.
Tokyo Electric Power Co's two nuclear plants in Fukushima reported no new irregularities after the quake, Kyodo news agency said. Onagawa nuclear plant in Miyagi prefecture further north also detected no irregularities, operator Tohoku Electric Power Co said.
In Miyagi prefecture, where the shaking was the strongest, there were no information on injuries, Kyodo added.
The United States Geological Survey recorded the quake at 6.1, with a depth of 20.5 miles. The epicentre of the quake was off the coast of Fukushima prefecture, more than 200 km (125 miles) northeast of Tokyo, where buildings also shook.
A magnitude 9 earthquake in March 2011 in the northeast triggered a tsunami which killed about 16,000 people, with a further 3,000 still missing. The disaster caused meltdowns and crippled the Fukushima Daiichi nuclear plant.