Thousands of people evacuated from parts of northern Japan as the country's largest wildfire in three decades raged unabated Sunday after killing at least one person, officials said.

Around 2,000 people fled areas around the city of Ofunato in Iwate Prefecture to stay with friends or relatives, while more than 1,200 evacuated to shelters, according to officials.

"We're still examining the size of the affected area, but it is the biggest since the 1992 wildfire" in Kushiro, Hokkaido, a disaster management agency spokesman told AFP Saturday.

Some reports estimated the fire had spread over 1,800 hectares.

Aerial footage by NHK showed columns of white smoke billowing, four days after the blaze first materialised, with military helicopters trying to douse them.

One burned body has been discovered so far, with more than 80 buildings damaged and around 1,700 firefighters mobilized from across the country.

The number of wildfires has declined since the peak in the 1970s, according to government data, but there were about 1,300 across Japan in 2023 -- concentrated in the February to April period when the air dries and winds pick up.