A strong earthquake struck the same Japanese coast that was devastated by last year's massive quake and tsunami, but despite understandable fears it generated only small waves, with no immediate reports of heavy damage.
Several people along the north-eastern coast were injured and buildings in Tokyo and elsewhere swayed for several minutes. After the earthquake, the authorities issued a warning that a tsunami potentially as high as two metres could hit. Sirens rang out along the coast as people ran for higher ground.
In the event, Ishinomaki, a city in Miyagi, reported a tsunami one metre high and other towns reported smaller tsunamis.
The earthquake had a preliminary magnitude of 7.3 and struck in the Pacific Ocean off Miyagi prefecture at 5.18pm local time, the Japan Meteorological Agency said. The epicentre was 6.2 miles beneath the seabed and 150 miles offshore. The area was shaken by repeated, smaller aftershocks.
About two hours after the quake struck, the tsunami warning was cancelled, with the Pacific Tsunami Warning Centre saying there was no risk of a widespread tsunami.
The UN atomic agency said it had been informed by Japanese authorities that no problems had been detected at nuclear power plants in the region nearest to the epicentre of the earthquake, which came as a relief following the disastrous meltdown at the Fukushima plant last year.
The International Atomic Energy Agency said its Incident and Emergency Centre had been in contact with Japan's Nuclear Regulation Authority "to collect information about the status of … nuclear power plants that could be affected".
Japan has barely begun to rebuild from last year's magnitude-9.0 earthquake, which triggered a tsunami that swelled to 20 metres high in some areas and killed 19,000 people.