At least 18 people died when a passenger bus (Na 4 Kha 4970) en route to Kalikot from Jumla plunged some 150 metres down the road into Tila River along the Rararihi road section.
Police said all the injured have been taken to hospitals.
The bus was driving on a narrow mountain road when the accident happened about 10 kilometers west of the Joomla, Katmandu.
The incidents of road mishaps have increased in the recent past across Nepal.
The deadly accidents are attributed to poor road conditions, old vehicles and negligence of drivers.
