7.22am: Japan has been rocked by a series of earthquakes causing a major Tsunami. Here's some details from our Japan correspondent, Justin McCurry:

A series of powerful earthquakes struck north-east Japan on Friday afternoon, triggering warnings of tsunami as high as 10 metres and shaking buildings in Tokyo.

The first earthquake struck at 2:46pm local time and measured magnitude-8.8, according to the US geological survey. Within 30 minutes the same region was rocked by two more big quakes of slightly lower intensity, Japanese news reports said.

The first quake, Japan's biggest for seven years, struck at a depth of six miles about 80 miles of the eastern coast, according to Japan's meteorological agency.

The Pacific tsunami warning centre in Hawaii said a tsunami warning was in effect for Japan, Russia, Marcus Island and the Northern Marianas. A tsunami watch has been issued for Guam, Taiwan, the Philippines, Indonesia and Hawaii.

All flights in Japan were grounded immediately after the quake while officials checked for runway damage. Strong tremors were felt in Tokyo about 30 minutes after the quake. Newsreaders in the capital wore helmets as they gave updates, while office workers rushed out of buildings on to the street.

Television showed a building on fire in the Odaiba district of Tokyo, although it was not immediately clear if the blaze was connected to the earthquake.

Other footage showed water levels rising quickly in the coastal town of Miyako in Iwate prefecture on Japan's north-east Pacific coast. Public broadcaster NHK showed cars, trucks, houses and buildings being swept away by tsunami in Onahama city in Fukushima prefecture. 

TV news presenters repeatedly warned people on the Pacific coast to head for higher ground.

In a land of people used to earthquakes, everyone is saying this one, which hit at 14:46 local time, is the strongest they’ve ever felt-and that’s in Tokyo, some 400 kilometers southwest from the epicenter.

Scientists are calling it the biggest earthquake in Japan’s tremor-filled history. Preliminary estimates from the USGS put the magnitude at 7.9, which have since grown to 8.9. Estimates of the depth range from 10-20 kilometres. This earthquake was 178 times as powerful as the 1995 Hanshin/Kobe earthquake.

Miyagi prefecture was pummeled the hardest. There Japan’s earthquake intensity scale, which measures the amount of shaking at ground level, recorded a 7, the highest level. More than 20 deaths have been reported.

Tsunamis reaching 10 metres have hit the area and 3 metres tsunami are reported down all the way down the coast far past Tokyo.

Panic gripped Tokyo as bookshelves and installations in offices fell, people poured into the streets and more than a dozen buildings reported fire sending smoke billowing into the sky.

Trains are stopped as far down as Shizuoka, far south of Tokyo. Some phone lines are dead, but my internet is working. I’m writing minutes after the earthquake, stuck on a train that screeched to a halt and then bounced on the tracks.