Hundreds of firefighters were battling wildfires in the forests of northern Japan on Saturday, as authorities urged more than 3,200 people to evacuate from their homes, government officials said.

As of Saturday morning, blazes in the mountainous areas of Iwate region had burned about 700 hectares (1,730 acres) since breaking out three days ago, local government officials said in a statement.

A large column of smoke, which could be smelled 30 kilometres (20 miles) away, was seen rising up the valley near the town of Otsuchi as two helicopters dropped water on the burning forest.

In Otsuchi, fire engines were spraying the forest near homes close to the fire.

About a dozen helicopters and more than 1,300 firefighters as well as Japan Self-Defense Forces troops would be mobilised on Saturday to battle the fires, the statement said.

At least eight buildings had been burnt but all the residents had evacuated, it said.

"We're making efforts to extinguish (the fires) ... and will update the information" later in the day, an Iwate official told AFP.

"Ultimately, I do hope it'll rain," a man in Otsuchi told public broadcaster NHK.

Increasingly dry winters have raised the risk of wildfires. A blaze that broke out in the Iwate city of Ofunato early last year was Japan's worst in more than half a century.

Scientists have long warned that climate change caused by mankind's burning of fossil fuels will make periods of drought more intense and longer-lasting, creating the ideal conditions for wildfires.