It is a “race against time” for rescuers searching for scores of victims trapped under rubble as Japan reels from its second major earthquake in two days, Prime Minister Shinzo Abe has said.
At least 25 people have been confirmed dead and more than 1,000 injured after the 7.3-magnitude earthquake hit southwestern Japan in the early hours of Saturday morning.
The number of casualties is expected to rise as rescue workers dig through collapsed buildings, mud and debris.
“Nothing is more important than human life and it’s a race against time,” said Mr Abe.
“Daytime today is the big test,” he added.
The epicentre of the quake was near the city of Kumamoto on the southern island of Kyushu, the same region hit by a 6.2 tremor which killed nine people barely a day earlier.
Rescue efforts have been hindered by damage to the region’s transport network, with one tunnel caved in, a highway bridge damaged, roads blocked by landslips and train and air services halted.
The number of military personnel sent to the area has been increased to 20,000.
Heavy rain and strong winds forecast for the next few hours are threatening to further complicate the emergency response.
It is feared that rainfall hitting soil loosened by the quake could set off further mudslides in isolated rural towns, where people in collapsed homes are waiting to be rescued.