A seven-year-old boy who went missing after his parents left him in a Japanese forest "as punishment" has been found alive and unharmed.

A police spokesman said Yamato Tanooka was discovered by a soldier at a military base in northern Hokkaido island.

Manabu Takehara, a spokesman for the Self-Defense Forces, said the boy "looked in good health", adding that he was taken to hospital by helicopter for a medical check.

It is understood he will remain in hospital overnight as a precaution.

Speaking outside the hospital, the boy's father apologised and thanked rescuers who took part in the search.

"My excessive act forced my son to have a painful time," he said.

"I deeply apologise to people at his school, people in the rescue operation, and everybody for causing them trouble".

According to the police spokesman, the boy "walked through the mountains" until he found the army building, broadcaster NHK reported.

He also reportedly drank water and slept on mattresses spread on the floor.

Army personnel, emergency services and volunteers had been searching for the boy since Saturday.

His parents initially said they had lost him when they were out hiking to gather wild vegetables.

They subsequently admitted they made him get out of their car on a mountain road for misbehaving.

The boy was abandoned on the northern side of the road on a slope of Mount Komagatake, which rises to an altitude of 1,131 metres (3,710 feet).

He was reportedly without food or water.

Police have said they are considering filing charges against the boy's parents, according to Kyodo News.