A father has been reprimanded by police in Japan after leaving his seven-year-old son alone on Mount Fuji while continuing towards the summit with his older child.

The 48-year-old man from Nagoya was climbing the Fujinomiya Trail with his two sons on August 20 when the younger boy became tired near the sixth station, about 2,500 metres above sea level.

The father reportedly told him to “wait here” before continuing uphill with his older son, aged about 12 or 13.

A mountain hut worker discovered the boy sitting alone on a bench at around 7:40 AM, according to reports. The worker brought him inside and contacted police.

Rain was falling and fog was developing at the time, raising concerns about rapidly changing conditions on Mount Fuji. The child was unharmed.

Police eventually contacted the father, who had reached near the eighth station, and ordered him to return for his son.

Authorities reprimanded the man and warned that leaving a young child behind was unacceptable, even if it meant abandoning the climb.

“I made a rash decision, and I deeply regret it,” the father reportedly told police.

Authorities also urged hiking groups to remain together and plan climbs around the person with the least stamina.