Japanese officials say at least 27 people were killed and 10 are missing after landslides buried dozens of houses in the outskirts of Hiroshima.
Television footage on Wednesday showed residents and rescue workers searching through the rubble of suburban homes for survivors.
Japanese Prime Minister Shinzo Abe has ordered several hundred soldiers to the area to help with rescue efforts.
The area received about 24 millimeters, or about a month's worth, of rain within a 24-hour period, loosening hills already soaked by recent storms.
Forecasters warn that more rain is expected, saying there is a continued risk of flooding and landslides.
Landslides pose a major risk in crowded Japan, where many homes are built on or near steep slopes.