Emergency response crews from Japan's defense force were dispatched to the central city of Atami after landslides triggered by heavy rains left at least 20 people missing, public broadcaster NHK said on Saturday.

Prime Minister Yoshihide Suga has called together an emergency task force to respond to the crisis, NHK reported, as it aired Twitter footage showing floods destroying houses and washing away debris.

The rainfall deluging the city since Friday has already exceeded the average July levels for both Shizuoka, where Atami is located, and neighbouring Kanagawa prefecture, according to NHK.