A powerful earthquake with a preliminary magnitude of 7.1 struck southern Japan early on Saturday morning, barely 24 hours after a smaller quake hit the same region and killed nine people.
Japanese broadcaster NHK said a number of calls were coming in from residents reporting people being trapped inside houses and buildings.
The quake shook the Kumamoto region at 1:25 AM Saturday, and several aftershocks soon followed. Japan's Meteorological Agency issued an advisory for a tsunami up to 1 metre high along the coast west of the epicentre in Kumamoto; the advisory was lifted less than an hour later.
Sirens of patrol vehicles were heard on the background as NHK reported from the hardest-hit town of Mashiki. The asphalt ground outside the town hall had a new crack, apparently made by the latest earthquake.
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. Friday's weaker, magnitude 6.5 earthquake brought down buildings and injured about 800 people, in addition to the nine deaths.
The epicenter of the latest earthquake was about 12 kilometres northwest of Friday's, and at a depth of about 10 kilometres. Saturday's's quake was more shallow.
It hit residents who were still in shock from the previous night's horrors and had suffered through more than 100 aftershocks in the interim.
Yuichiro Yoshikado described the horror of the earthquake striking as he was taking a bath in his Mashiki apartment.
"I grabbed onto the sides of the bathtub, but the water in the tub, it was about 70 per cent filled with water, was going like this," he said, waving his arms, "and all the water splashed out."
"It's as if all control was lost. I thought I was going to die and I couldn't bear it any longer."
A bright spot broadcast repeatedly on television on Saturday was the overnight rescue of an apparently uninjured baby, wrapped in a blanket and carried out of the rubble of a collapsed home.
Police said on Saturday that concern about aftershocks was keeping many people from starting the huge task of cleaning up. Since Saturday's quake was bigger, Friday's was technically a foreshock.
Yoshikado, whose building was undamaged despite the intense shaking, checked the damage at his aunt and uncle's home nearby. Kitchenware was scattered on the floor, and a clock had stopped around 9:26 pm, the time of the earthquake.
Power and water have yet to be restored, and many in the neighborhood have yet to return because of the aftershocks.
The epicentre was 120 kilometres northeast of Kyushu Electric Power Co.'s Sendai nuclear plant, the only one operating in the country.