The plant, operated by Tokyo Electric Power Co, was shut down earlier on Friday.
The Fukushima prefecture warned those living in the vicinity of the plant of possible radiation leaks.
Several nuclear plants elsewhere along the coast were also partially shut down, with no reports of leakage.
The death toll from the earthquake and subsequent tsunamis in Japan has exceeded 200. Many people have been injured and many are still missing.
The 8.9-magnitude quake that struck off the eastern coast of Japan earlier on Friday was followed by a series of powerful aftershocks.
A tsunami more than 7.3 meters high hit the Soma port in the Fukushima Prefecture, while a tsunami more than four meters high hit the ports of Kamaishi and Miyako in Iwate Prefecture, the country`s Meteorological Agency said.
NHK TV showed footage of waves sweeping away buildings and vehicles as far as 1.5 km inland. Airports were closed down and train services suspended. More than 4 million homes are without power.
The Kyodo Japanese news agency said a ship with some 100 people on board was washed away.
Kyodo news agency reported explosions at two major Nissan factories and a fire in a turbine building at the Onagawa nuclear power plant in Miyagi prefecture. There was also a fire at an oil refinery in Ichihara city in Chiba prefecture near Tokyo.
The quake is the strongest to hit Japan in 78 years, the head of the Russian Hydrometeorological Center, Alexander Frolov, said in an interview with Russia`s Rossiya 24 TV channel.
The country`s Meteorological Agency is urging people in quake-hit areas to evacuate to higher ground to avoid further tsunamis.
More earthquakes measuring over 7.0 on the Richter scale could occur in and around Japan within a month, the Meteorological Agency said.
At least 19 countries and Pacific islands have issued tsunami warnings. (*)
Editor: Kunto Wibisono
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