A strong earthquake with a preliminary magnitude of 5.6 jolted areas north of Tokyo Tuesday, the Japan Meteorological Agency said.
There were no immediate reports of casualties and major damage. No tsunami warning was issued for the 12:28 p.m. (0328 GMT) quake, the agency said, adding that the tremor was also observed in central Tokyo.
Operators of nuclear power plants in the affected areas, including the crippled Fukushima Daiichi nuclear complex, said there were no signs of abnormalities at the facilities from the quake.
Shinkansen bullet train service in the region was briefly suspended to confirm safety, but resumed afterwards. No damage was reported at Tokyo's Haneda International Airport.
The focus of the earthquake was 50 kilometers underground in southern Ibaraki Prefecture, northeast of Tokyo, the weather agency said. It registered a lower five on the Japanese seismic scale of seven in parts of Tochigi, Gunma and Saitama prefectures around Tokyo.
The weather agency defines an intensity of lower five as strong enough to make hanging objects swing violently and most unstable ornaments fall.
Japan is one of the world's most earthquake-prone countries, accounting for about 20 percent of the world's earthquakes of magnitude six or greater.