An earthquake with a preliminary magnitude of 6.9 has struck off the coast of Fukushima prefecture in Japan.
A tsunami warning of up to 3 metres (10 feet) was issued and at multiple points on the eastern coast waves of up to 90 centimetres were observed.
The Japan Meteorological Agency (JMA) says the quake struck around 6am at a depth of 10 kilometres.
A water cooling system for Fukushima Daini nuclear power plant's third reactor has broken, but there is enough coolant in the reactor so it currently poses "no immediate danger", Japan state broadcaster NHK reported.
The US Geological Survey had a preliminary magnitude of 7.3, but then revised the figure down to 6.9. The JMA then revised their calculation of the magnitude of the quake up to 7.4.
The earthquake shook buildings in Tokyo, 240 kilometers (150 miles) southwest of the epicentre.
NHK urged the public to evacuate and the government has set up a tsunami advisory.
Japanese prime minister, Shinzo Abe, said the government would do its utmost to respond to the quake, Reuters reported.
"Please do not think that you are safe. Please evacuate to high grounds," the network said. "Even if you live inland please go and evacuate."
There were reports that a fire has broken out at a chemical factory in the Fukishima prefecture.
Fukushima prefecture is north of Tokyo and home to the nuclear power plant that was destroyed by a huge tsunami following an offshore earthquake in 2011.
Tohoku Electric said that it found no abnormalities at its Onagawa nuclear power plant after the earthquake.
A Tsunami alert has been issued for coasts within 300 kilometres of the earthquake's epicentre.
There are reports of minor injuries.
Earthquakes are common in Japan, where around 20 percent of the world’s earthquakes of magnitude 6 or greater occur.
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