Searchers in northern Japan spent a third day on Monday looking for a seven-year-old Japanese boy who went missing after his parents left him in a forest to teach him some discipline.

At least 130 firefighters and police officers were scouring the woods near Nanae town in Hokkaido, looking for Yamato Tanooka, media reported.

Tanooka's parents initially told police they were picking wild plants when Yamato went missing on Saturday. However, they later admitted to police they had intentionally left the boy in the forest to discipline him after he threw rocks at people and cars earlier in the day, Japanese television stations reported.

Tanooka's parents said they drove about 500 metres (yards) away and when they returned shortly after they couldn't find their son, who was last seen in a t-shirt and jeans.

Media reported that overnight temperatures in the forest have dropped to 7 degrees Celsius (45F).