A major earthquake collapsed buildings and sparked fires in Japan's southwest.

A "considerable number" of people have reportedly died in a shopping mall damaged by a major earthquake in southwestern Japan on Tuesday, broadcaster TBS said.

Earlier police told AFP that they could not confirm whether there were any fatalities at the mall in the town of Kashima.

Emergency services earlier said that "many people" were trapped inside the building after a floor collapsed.

In "Kashima town, a shopping complex's second floor collapsed, leaving many people trapped inside," the fire department said in a statement.