A seven-year-old boy missing since his parents abandoned him in a bear-inhabited forest in northern Japan nearly a week ago as a punishment has been found alive, a rescuer said.

Sorry, this video has expired Boy's father says his actions were 'really excessive'

The boy, apparently unharmed and in good health, was discovered inside a military base about 7:50am (local time), a police spokesman in northern Hokkaido island, Tomohito Tamura, said.

"A Self-Defence Forces official who was on a drill found a boy whose age appeared to be seven," Mr Tamura said, adding that the boy's parents were reunited with him and confirmed he was their son.

"There was no conspicuous external injury, and the boy introduced himself as Yamato Tanooka."

A Self-Defence Forces member told NHK national television: "One of our soldiers was preparing for drills this morning and unlocked the door of a building on the base, and there he was.

"When he asked 'Are you Yamato?' the boy said 'yes'.

"Then he said he was hungry, so the soldier gave him some water, bread and rice balls.

"There were [mattresses] placed on the floor inside the building and when the man who found him asked 'How were you sleeping?' he said he was sleeping between them."

Boy took shelter in hut 5.5km from where he went missing

Members of a search party celebrate after the boy is found. ( Reuters: Kyodo )

The boy told police he walked to a hut inside the military base on Saturday night and took shelter there, Local newspaper Hokkaido Shimbun reported.

The base is reportedly located some 5.5 kilometres north-east of the site where he went missing.

The boy somehow managed to survive for nearly a week in the densely forested area, where night temperatures fell as low as 7 degrees Celsius and heavy rain had fallen, despite wearing only a t-shirt and jeans.

Nippon TV said there was a tap outside the building and that the boy had been drinking water from it while he sheltered there.

Yamato was taken to hospital for a check-up but was healthy except for low body temperature and would be kept overnight as a precaution, a doctor told a news conference.

Police considering charging parents with neglect

A tearful Takayuki Tanooka, the boy's father, thanked rescuers for their efforts and apologised for causing trouble.

"We've reflected on what we did and it was really excessive. We loved him before, but I hope to give him even more attention now," Mr Tanooka said.

He related the emotional reunion in a television interview, saying he had apologised to his son.

"First of all, it's really great he is safe. I can't find words. It's good," he said.

The boy's parents initially said he disappeared while the family foraged for edible plants on Saturday, but later told police they forced him to stand by the roadside to discipline him for throwing stones at people and cars.

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

Sorry, this video has expired Searchers comb through a forest in Japan looking for a missing 7-year-old boy

The area is so remote, residents of the region said they rarely go through it.

Japanese media interrupted regular programs to broadcast news of the stunning development in the case, which has drawn huge media attention and criticism of the parents' actions.

Police have said they are considering filing neglect charges against his parents, according to Kyodo News.

"We have done an unforgivable thing to our child, and we have caused a lot of trouble for everyone," Mr Tanooka told television reporters earlier.

A search crew of 200 people had been looking for him since Saturday afternoon.

Police rescuers and fire personnel initially led the search for the boy but after coming up empty-handed the local town of Nanae requested military support.

From Wednesday Japanese soldiers joined in the hunt in the rugged region, where heavy rains at times hampered the operation conducted in overgrown forest and through tall bushes.

ABC/wires