Searchers are continuing to comb a forest in Japan for a missing seven-year-old boy left alone in the woods by his parents as punishment for being naughty.

Police on horseback were among 130 rescuers searching a mountainous area of the northernmost island of Hokkaido from dawn for Yamato Tanooka, who went missing on Saturday.

His parents first said he had disappeared while the family foraged for edible plants. They later told police they had left him by the road to discipline him after he threw stones at people and cars.

They said they drove about 500m down the road but when they went back a few minutes later he had disappeared.

The area is so remote that residents of the region say they rarely go through it.

"We have done an unforgivable thing to our child, and we have caused a lot of trouble for everyone," Yamato's father, Takayuki Tanooka, told television reporters. "I just hope he is safe."

Heavy rain is forecast for tonight and Yamato was wearing only a T-shirt and jeans.