The bus, with nearly three dozen pilgrims, was headed for the famous Muktinath temple when it turned turtle in Mustang district yesterday, Chief District Officer Bhim Raj Pokharel said.
Security personnel and a Nepal Army helicopter were rushed to the spot for rescue and relief operations.
The bus driver was also injured in the accident which was apparently caused due to the poor road infrastructure in the remote mountainous region, the official said.
Muktinath is a famous Hindu and Buddhist pilgrimage site as well as a popular tourist destination.