Japan's military joined the search for a 7-year-old boy abandoned in a dense northern forest by his parents as punishment for being naughty.

Seventy five members of the Self-Defence Forces joined 200 police and civilians beating their way through thick brush in the mountainous forest on Hokkaido Island.

A local hunter was also added to the search for Yamato Tanooka after fresh bear tracks were found in the area where he vanished at the weekend, Jiji news agency said.

The boy's parents first said he disappeared while they foraged for edible plants, but later told police they had left him by the road to discipline him after he threw stones at people and cars.


They said when they drove back a few minutes later the boy 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."

Despite the larger search party no leads turned up, with many worrying the boy might not have survived heavy rains which fell on Wednesday. He was last seen wearing a T-shirt and jeans in an area where the overnight temperatures can fall as low as 7C.

The search has gripped Japan, with news programmes offering hourly updates, and thousands have taken to the internet to both pray for the boy's survival and excoriate his parents for what is seen as neglect.

"If I was a small child in this situation I would either run after the car or wait there until they came back. I just hope he is safely found," one person wrote.

- Reuters