The search for a boy who disappeared after his parents left him behind in a Japanese forest as punishment has pushed into a fifth day, but with no clues to his fate.

Yamato Tanooka, 7, has been missing since Saturday after his parents made him get out of their car as punishment for misbehaving, leaving him behind in a wooded area on Hokkaido, Japan's northernmost main island.

Police said Thursday's search by more than 180 rescuers, including defense troops, focused on the area where the boy was believed to have been dropped off, and revisiting and combing through the woods.

Police said the parents admitted they made the boy get out of the car as "discipline," after changing their earlier story that the boy disappeared while picking wild vegetables.