Japanese emergency workers searched tirelessly for survivors at a wrecked shopping mall on Thursday, as the death toll from a major earthquake hit 34 and tens of thousands were left without power in punishing heat.

The Kumamoto disaster management office issued the new tally for Tuesday's quake, with seven bodies now extracted from the mass of rubble, steel and wires of the Aeon shopping mall after a suspected gas blast.

Eight people were also confirmed dead at the Nippon Paper Industries factory in Yatsushiro city, where part of a red-and-white smokestack collapsed, according to the office.

Five others were in a critical condition after the 7.1-magnitude tremor, while almost 9,500 locals were in evacuation centres in the region of southwestern Japan on the island of Kyushu.

The quake caused widespread damage, flattening homes, damaging bridges, triggering fires and leaving tens of thousands of residents without power and water in temperatures forecast to hit 38 degrees Celsius this weekend.

Some 13,520 households remained without electricity on Thursday.

Hundreds of elderly people – Japan has the world's second-oldest population – slumbered on thin mats on the hard lobby floor at one community centre in Uki city as they sought relief from the searing sun.

"Thank God for these shelters," said one woman, who declined to give her name, as people slept between chairs and tables or gathered around a television.

At home or in the car "it's too hot and there are too many mosquitoes," she said.

"In this heat, if you don't have electricity and air conditioning, it's very tough," father-of-four supermarket employee Hiroyuki Matsushima, 53, said.

TV footage showed people queueing for petrol and drinking water. Authorities have sent hundreds of air conditioning units to shelters. (AFP)


Edited by Aaron Tam