Around 175 residents of the Saganoseki district of Oita city, some 770km southwest of Tokyo, fled to an emergency shelter after the blaze broke out at approximately 5.40pm yesterday (local time), the Fire and Disaster Management Agency said.
One person was still missing while the cause of the fire was under investigation, it said.
Aerial footage from local broadcasters showed houses reduced to rubble and thick plumes of smoke rising from the hilly town, which overlooks a fishing harbour renowned for its premium Seki-brand mackerel.
Local media reported the flames had also spread to nearby forested slopes.
A military firefighting helicopter was dispatched at the request of the Oita prefecture governor, Japanese Prime Minister Sanae Takaichi said in a post on X.
