A strong earthquake with a preliminary 6.0 magnitude jolted Japan's Fukushima Prefecture and its vicinity early on Friday.
The epicenter of the quake, which occurred at 03:22 a.m. local time, was some 50 kilometers under the sea off the prefecture, following a report of the Japan Meteorological Agency (JMA), as cited by the Xinhua news agency.
No tsunami alert was issued and no immediate damages were reported.
Strong tremors were also felt in Tokyo, but Tokyo Electric Power Co Inc, the operator of the troubled Fukushima-1 nuclear facility, said there were no irregularities in the plant's operations.