At least 19 people died and more than 1,000 were injured in a magnitude-7.3 earthquake that struck the southern Japanese island of Kyushu early Saturday, while a series of aftershocks rattled the region, authorities said.
Dozens more were trapped or buried under rubble, and the government was to increase the number of troops to be dispatched to the region to 20,000 within two days, from 2,000 already on site, Chief Cabinet Secretary Yoshihide Suga told a news conference.
Two university students have been confirmed dead after they were buried under a leveled apartment building in Minamiaso village, broadcaster NHK reported, while many others also died after they had been trapped under collapsed houses.
The quake, first estimated at a magnitude of 7.0, hit after nine people were killed and 1,100 injured in a magnitude-6.5 earthquake Thursday in the same region - the strongest in five years.
Saturday’s quake occurred at 1:25 am (1625 GMT Friday) with its epicentre in the Kumamoto prefecture at a depth of 12 kilometres, and was followed by a series of aftershocks, the Meteorological Agency said.
More damage to houses and buildings were reported Saturday in the prefecture's town of Mashiki, the hardest-hit area of the tremor Thursday evening, 900 kilometres south-west of Tokyo.
TV footage showed flattened houses, collapsing apartment buildings, cracks on roads and a large-scale landslide in Minamiaso village, 20 kilometres to the east of Mashiki.
A 200-metre-long bridge plunged into a valley and the city hall collapsed in Uto, in the south-west of the prefecture and 5 kilometres from the sea. Kumamoto Airport, 15 kilometres north-west of Mashiki, was closed after the ceiling fell, NHK reported.
Meteorological agency officials detected a small eruption at Mt Aso in Kumamoto at around 8:30 am (2330 GMT Friday), but they had not concluded whether the active volcano's most recent eruption was linked to the recent tremors, they said.
Across the prefectures of Kumamoto, Miyazaki and Oita, the quake cut off water supply to about 385,000 households and more than 200,000 households lost electricity, Kyodo News agency reported.
Nearly 70,000 evacuees were staying at 655 temporary shelters in Kumamoto prefecture, Kyodo said.
There have been more than 260 aftershocks since the magnitude-6.5 Thursday evening, the agency said. Saturday, some of them hit the central part of Oita prefecture, east of Kumamoto, it said.
Gen Aoki, director of the earthquake and tsunami department of the meteorological agency, said Thursday’s tremor was now considered to be a “precursor to the main quake” early Saturday.
More aftershocks and mudslides were a risk amid expected heavy rain and strong winds later in the region on Saturday, he told a press conference.
There were no abnormalities at three nearby nuclear power stations, including the Sendai Nuclear Power Station in Kagoshima prefecture, Suga told a news conference.
The Sendai plant is 130 kilometres south of Kumamoto. Kyushu Electric Power restarted two nuclear reactors last year, the country's first under updated regulations.
This week’s quakes were strongest since the earthquake and resulting tsunami in the north-east on March 11, 2011, which prompted Japan to turn off all of its workable reactors in following months, before the two at Sendai were restarted.
Those twin natural disasters killed about 18,500 people and triggered the nation’s worst accident at the Fukushima Daiichi Nuclear Power Station.
Earthquake- and volcano-prone Japan sits at the convergence of four tectonic plates.