A massive earthquake has struck off the eastern coast of Japan's main Honshu Island, measuring 6.7 on the Richter scale.
The earthquake just before 2am on Thursday was followed by a series of tremors, Japan's meteorological agency said.
In the capital, Tokyo, which is north of the epicentre of the earthquake, buildings swayed.
The impact was strongest in the Ibaraki and Tochigi regions, north of Tokyo, where holes and cracks emerged in weaker buildings.
Al Jazeera's Tony Cheng, in Tokyo, said that aftershocks were occurring there, with buildings shaking considerably.
"It doesn't seem to be having any serious affect," he said.
"As I look out of the window there's still a lot of traffic going down the highway.
"It does feel from the aftershocks we are getting here in our hotel that it was a massive quake.
"If that happened a significant distance off the coast, there shouldn't be any significant damage.
"But to shake this building as much as it is at the moment one would imagine there is some structural damage.
"Tokyo is quite far from the centre of the quake, but there may be areas closer which have been badly affected."
Earthquakes are common in Japan - the country experiences 20 per cent of the world's major quakes.