A magnitude 7.1 earthquake hit southern Japan on Friday - the second powerful temblor in less than 24 hours - with reports of people being trapped in fallen buildings and houses.
The quake struck Kumamoto prefecture at a depth of 40km, shaking the region as a series of aftershocks followed on the southern island of Kyushu.
Japan's Meteorological Agency issued an advisory for a tsunami up to one metre high along the coast, but it was lifted less than an hour later.
It was the second major tremor to rock Japan's south in 24 hours after a 6.2 quake hit near Mashiki town on Thursday, killing nine people and injuring about 1,000 others.
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"We have just been woken up by a very large earthquake in the main town of Kumamoto. Things were thrown about in the hotel," said Al Jazeera's Rob McBride, reporting from Mashiki near the epicentre.
"We can't see much damage, but we feel very large aftershocks."
Japanese broadcaster NHK said a number of calls were coming in from residents reporting people being trapped in structures.
The Nuclear Regulation Authority said no abnormalities were found at the Sendai nuclear plant, where the only two of Japan's 43 operable reactors are online.
According to the Japan Meteorological Agency, Mashiki sits near two faults on Kyushu. The area is also near Mount Aso, a huge, active volcano, but officials said the quake was unusually strong for Kyushu.
"There is a great possibly that the damage will spread widely so we must give it our all to gather the information on the damage situation and make the rescues and relief," Prime Minister Shinzo Abe said on Saturday.
After Thursday's temblor, more than 3,000 troops, police, and firefighters were dispatched to the area from around Japan. About 44,000 people stayed in shelters.
Residents were still in shock from the previous night's horrors and had suffered through more than 100 aftershocks.
Japan is frequently hit by major quakes. In March 2011, a 9.0-magnitude earthquake led to a devastating tsunami that killed 18,000 people along Japan's northeast coast.
The wave struck the Fukushima nuclear plant, causing a major radiation leakage.
More than 100,000 displaced people are still unable to return to their homes near the nuclear plant because of the contamination.
| Powerful earthquake rocks southern Japan