The vehicle was travelling through Mugu district when it left the road and plunged down a hillside shortly after midday on Tuesday, local media report.
The cause of the crash is unclear, but some reports suggest the bus may have had an issue with its brakes failing.
Many passengers on the bus were returning home from various parts of the country to celebrate the Vijayadashami festival. Mugu is famous for the beautiful Rara lake, which lies 650 km North-West of Kathmandu. Images published by local media showed rescue workers carrying people and what appeared to be personal belongings such as travel bags.
They added that many of those on the bus may have been travelling home after celebrating Dashain – a major religious festival in Nepal and India.
More than a dozen people were being treated for injuries, with some airlifted to a nearby hospital.
It is not clear how many people were travelling on the bus when it veered off the road, but police said the death toll could rise further.
– BBC