An earthquake with a preliminary magnitude of 6.2 jolted northern Japan today, the Japan Meteorological agency said, though there were no reports of damage and nuclear facilities in the area were unaffected.
The quake, at 12:33 p.m. (3.33am Irish time), was also felt in Tokyo.
The focus of the tremor was 40km below sea level off the east coast of Fukushima prefecture, on Japan's main island of Honshu, about 240 km northeast of Tokyo, the Japan Meteorological Agency said. No tsunami warning was issued.
Kyodo news agency said there was no injuries reported in either Fukushima prefecture or Miyagi prefecture to the north.
Tokyo Electric Power Co's Fukushima nuclear power plants were operating normally after the quake, a company spokesman said.
Tohoku Electric Power Co's Onagawa nuclear plant in Miyagi prefecture and Higashidori nuclear plant in Aomori also continued their normal operations, company officials said.
Nippon Oil's Sendai refinery in Miyagi was continuing normal operations after the quake and there were no reports of damage, a refinery official said.
Japan Energy group refinery Kashima plant in Ibaraki prefecture, south of Fukushima, has been shut for scheduled maintenance and no damage was reported, a plant official said.
Sendai airport Miyagi prefecture halted flights briefly to check the runway before resuming operations, national broadcaster NHK said.
The bullet train that connects Tokyo and Aomori, northern Japan, temporarily suspended operations on part of the rail network after the quake, Kyodo said.
Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.
In October 2004, an earthquake with a magnitude of 6.8 struck the Niigata region in northern Japan, killing 65 people and injuring more than 3,000.
That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400.
Reuters