Forty people have been confirmed dead, but the toll is expected to rise sharply. Another 39 have been reported missing. The government has issued a warning that another strong earthquake could hit Japan.
Japan said it was operating on an atomic power emergency footing but said no radiation leaks were detected among its reactors. The four nuclear power plants closest to the quake have been safely shut down, the United Nations atomic watchdog said Friday.
A 10-metre tsunami has hit the city of Sendai city, according to media reports, and a tsunami alert is in place all the way down the Pacific coast.
The quake struck 370 km from Tokyo at a depth of 24 km. It was felt as far away as Beijing. Officials are warning the tsunami could reach 10 metres high. Waves have hit Tokyo.
The Pacific Tsunami Warning Centre, west of Honolulu, Hawaii, issued a widespread warning extending across virtually the entire Pacific Ocean, including Australia, Antarctica and South America.
Minor tsunamis reached Taiwan's coastline without causing any damage, according to Taiwan's central weather bureau.
Coastal areas in Hawaii, which is some 4,000 miles east of the epicentre, are being evacuated.
“We have about four hours to evacuate the coast,” said John Cummings from Honolulu emergency services.
The first waves are expected to hit at 12h55 universal time. Indonesia is likely to be hit by waves at 11h00 universal time.
The Philippine government on Friday strongly urged residents of its Pacific coast to go farther inland.
Seismologists are warning that waves of up to a metre could hit there between 09h00 and 11h00 universal time.
There are fears that some low-lying islands in the Pacific could be completely submerged by the wave.
In Japan, Sendai airport is underwater and is closed as our several other airports, including Tokyo’s Hareda airport. Roads and train services closed and four million homes are without power.
Numerous injuries have been reported by police in Japan's Miyagi prefecture and there is widespread flooding in the area.
The quake struck off the north-east coast of the island of Honshu in the early afternoon, strongly shaking buildings in Tokyo. It triggered dozens of fires in Tokyo.
The Yokohama oil refinery has caught fire in Iichihara, near Tokyo.
Many were injured after a roof caved in during a school graduation ceremony at a hall in east Tokyo.
"People are remaining calm and gathering in earthquake centres and public parks away from tall buildings and wondering how they’re going to get home tonight," says correspondent Justin McCurry. "There are tens of thousands of people on the streets of Tokyo and public transport is still crippled."
He adds that it is difficult to gauge what the reaction has been in the worst-hit areas because there are problems with communication.
The car park at Tokyo Disneyland was drenched with water-logged segments from the ground due to liquefaction of soil caused by the tremor.
There were no injuries or property damage reported at the theme park.
Russian President Dmitry Medvedev on Friday offered his country's assistance to Tokyo,
as waves reached Kuril islands, which are the subject of a territorial dispute between the two countries.
Shares in the German insurance groups plunged in morning trading on Friday as they appeared set to bear heavy costs from the earthquake.
At 8.9 on the Richter scale, it is bigger than the 1995 Kobe earthquake in which more than 5,000 people died. Only six other earthquakes as powerful as Friday's have ever been recorded.
“Japan’s earthquake prepaeredness is fairly good, but I think it’s impossible for any country – even one with as advanced an infrastructure as Japan – to be fully prepared,” says McCurry.