The bus fell into a river at Chidipani village in Palpa district early Thursday morning, Xinhua reported.
The identities of the deceased are yet to be established. The injured passengers have been rushed to a local hospital.
“We are investigating the cause of the accident and rescue operations are going on,” police officer Shiva Kumar Shrestha said.
Local residents, police and army personnel are carrying out the rescue operations.
Bus accidents take place frequently in Nepal due to poor road conditions, lack of trained drivers and overloading of passengers.