Evacuees talk each other at a gym-turned shelter after an earthquake in Mashiki. Photo / AP
"Rescue operations at night will be extremely difficult ... It's a race against time," he said.
It has been reported that up to 422,000 households were without water and 100,000 without electricity.
National broadcaster NHK reported that 240,000 people had been given evacuation orders and there were fears landslides could wipe out parts of the affected region.
As evacuation centres filled to capacity the military were setting up tents and trucking in fresh water. NHK reported that 25,000 additional troops were set to arrive as well as more emergency services personnel and medical staff.
The death toll stood at 32 and the National Police Agency said 192 people had suffered serious injuries.
It was estimated 80 people were still trapped in rubble.