A strong earthquake with a magnitude of 6.9 has struck the coastal area of central Japan.
Initial reports say at least one person was killed and 100 injured in the quake that was felt as far away as Tokyo.
The authorities also issued a brief tsunami warning.
Several buildings collapsed and residents took cover in emergency shelters as the aftershocks continued to rattle Japan's main island of Honshu.
Japan's meteorological agency initially estimated the magnitude of the quake at 7.1 but later revised their figures.
A 52-year-old woman died after being hit by a block of stone and a total of 109 people were taken to hospital for treatment, including ten who were seriously injured, according to police.
The epicentre of the quake was located under the sea bed about 300km northwest of the capital Tokyo.
The government, which has set up a special earthquake information office, was to dispatch a team of inspectors to assess damage in the area, according to a government spokesman.
Japan lies at the junction of four tectonic plates and endures about 20% of the world's most powerful earthquakes, which frequently jolt Tokyo and other major cities.
The country prides itself on having one of the world's most accurate systems for assessing earthquakes and predicting tsunamis.
In December 2004, more than 220,000 people were killed when a massive tsunami battered nations along the Indian Ocean.
The tragedy led to worldwide calls for a more effective tsunami response system, including both the technology to predict the disasters and the means to get the message out.
Meanwhile, a second powerful earthquake also hit near Vanuatu in the southern Pacific.
