Aerial footage from public broadcaster NHK showed the bright blaze reducing several houses to charred frames in forested areas of Ofunato in the region of Iwate.

Nearly 600 nearby residents have been evacuated, according to the local municipality, with no injuries confirmed so far.

As of Thursday morning, city officials estimated that at least 84 buildings had been damaged by the fire, which the Self-Defence Forces were trying to extinguish from the sky.

Ofunato's mayor Kiyoshi Fuchigami described the fire as "large-scale" on Wednesday evening, saying around 600 hectares (1,500 acres) of land -- three times the size of Monaco -- had been burned.

The cause of the blaze remained unknown, he added.

There were about 1,300 wildfires across Japan in 2023, concentrated in the February to April period when the air dries out and winds pick up.

In the case of the latest Iwate fire, "strong wind" from the west helped spread a series of smaller wildfires in the same area, Fuchigami said.

One evacuee, a 45-year-old woman, told NHK that the fire had been approaching her house when she returned from work.

"I was relieved that my kids were safe," she said.

Another, a 32-year-old man, told the broadcaster it was "my first time to see a series of fires happen in such rapid succession".