The meteorological agency issued its top-level evacuation alerts for the entire Japanese coast, warning of a tsunami of up to six metres.
This tsunami engulfed the towns and farms around Sendai city in the northern Japan, and a four-metre wave swamped parts of Kamaishi on the Pacific coast.
Residents have been ordered to rush to high ground and stay away from the coast as tsunami can strike in several waves.
"An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines near the epicentre within minutes and more distant coastlines within hours," the agency said.
It also put the territories of Guam, Taiwan, the Philippines, the Marshall Islands, Indonesia, Papua New Guinea, Nauru, Micronesia and Hawaii under a lower tsunami watch.
The quake, already considered one of the worst in Japan's history, struck about 382 kilometres north-east of Tokyo at a depth of 10 kilometres, the US Geological Survey said.
Smoke could be seen rising from a building in Odaiba, a Tokyo suburb, and scores of cars are floating in Iwate prefecture harbour in northern Japan.
Police in Miyagi prefecture have reported numerous injuries.
Shinkansen bullet trains stopped when the quake struck, while the nuclear power plant in Miyagi prefecture stopped operating.
Power has been cut in Sendai city, where there are numerous reports of gas leaks.
Narita airport has temporarily closed and the runways are being inspected for damage.
The government has set up a crisis management team at the prime minister's office.
Japan's northeast Pacific coast, called Sanriku, has suffered from quakes and tsunamis in the past and a 7.2 quake struck on Wednesday.
In 1933 a magnitude 8.1 quake in the area killed more than 3,000 people. Last year fishing facilities were damaged after by a tsunami caused by a strong tremor in Chile.
Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.
This recent earthquake in Japan is recorded as the 7th largest earthquake in the world.
Source: .abc.net.au
Japan Earthquake Tsunami Picture (March 11, 2011)
Japan Earthquake Tsunami Picture (March 11, 2011)
Japan Earthquake Tsunami Picture (March 11, 2011)
Japan Earthquake Tsunami Picture (March 11, 2011)
Japan Earthquake Tsunami Picture (March 11, 2011)
Japan Earthquake Tsunami Picture (March 11, 2011)