Tsunami alert after quake off Fukushima
Long lines of cars formed as coastal residents followed government orders to flee to higher ground after a strong earthquake with a magnitude of 7.4 struck off the coast of Fukushima prefecture.
The Japan Meteorological Agency issued a tsunami warning for waves of up to 3 metres high in Fukushima and another prefecture, and a tsunami advisory for much of the rest of north-east Japan's Pacific coast. There were no immediate reports of damage or injury.
Tsunamis of up to 90cm were recorded about an hour after the earthquake at 6am local time, and the tsunami warning area was widened later in the morning.
Fukushima prefecture is home to the nuclear power plant that was destroyed by a huge tsunami following an offshore earthquake in 2011.
The operator of the Fukushima Dai-ichi plant said there were no abnormalities observed at the plant, though a swelling of the tide of up to 1m has been detected offshore.
Plant operator TEPCO said a pump that supplies cooling water to a spent fuel pool at the nearby Fukushima Dai-ni plant stopped temporarily, but that it was working again. The Tokyo-based utility is investigating the cause.
The US Geological Survey measured the magnitude at 6.9. The earthquake shook buildings in Tokyo, 240km south-west of the epicentre.
The meteorological agency said the quake struck at a depth of 10km.
It revised the magnitude upwards from an initial reading of 7.3.
National broadcaster NHK urged people to evacuate immediately, reminding them of the devastating 2011 quake that killed about 18,000 people.