A member of the Ground Self-Defense Force taking part in the annual cleanup of Himeji Castle, a UNESCO World Heritage site in western Japan, fell off an outer wall and suffered a broken leg Tuesday, local firefighters said.

The man in his 20s fell about 10 meters to the ground as his lifeline accidentally detached, according to the firefighters and police in Himeji.

Some 450 members of the GSDF were engaged in susuharai cleanup of the castle's outer walls and tiled roofs on the first day of the two-day annual operation from around 7:30 a.m.

The fire department received a call around 9:10 a.m. reporting one of the SDF members had fallen off a castle wall. The man was working on the east side of the outer walls.

Members of the GSDF's Camp Himeji have been conducting the end-of-year cleaning operation at the castle as part of training since 1976. About 900 members in total are joining the task through Wednesday.

The castle, built in its current form in 1609, was registered as a UNESCO World Heritage site in 1993.