A strong earthquake has shaken north eastern Japan, NHK TV said. A tsunami warning has been issued.
The US Geological Survey says it measured 7.8 on the Richter scale.
It was felt in Tokyo and reports from the capital suggest buildings have been swaying violently.
NHK television broke off regular programming to warn that a strong earthquake was due to hit shortly before it struck.
Afterwards, the announcer repeatedly urged everyone near the coast to flee to higher ground.
The magnitude-9.0 earthquake and ensuing tsunami that slammed into north-eastern Japan on March 11 last year killed or left missing some 19,000 people, devastating much of the coast.
All but two of Japan’s nuclear plants were shut down for checks after the earthquake and tsunami caused meltdowns at the Fukushima Dai-Ichi nuclear plant in the worst nuclear disaster since Chernobyl in 1986.
Immediately after today’s quake, there were no problems at any of the nuclear plants operated by Fukushima Dai-Ichi operator Tokyo Electric Power.