Authorities have long warned climbers to take care when attempting to scale Japan’s highest mountain, where hiking trails officially open next Monday.

Local police could not immediately confirm the reports to AFP, but public broadcaster NHK said the three were found near the volcano’s crater and were feared dead.

In Japan, a death must usually be confirmed by a doctor before it is reported by media outlets.

Mount Fuji is covered in snow most of the year, but during the July-September hiking season, more than 220,000 visitors trudge up its steep, rocky slopes.

Many climb through the night to see the sunrise, and some attempt to reach the 3,776m summit without breaks, becoming sick or injured as a result.

Regional officials have raised safety and environmental concerns linked to overcrowding on the mountain, a symbol of Japan and a once-peaceful pilgrimage site.

Hikers using the most popular route to climb Mount Fuji — the Yoshida trail — this summer will be charged ¥2,000 (US$13) each, with entries capped at 4,000 to ease congestion for the first time.