The landslide occurred around midnight on the Mandi-Pathankot national highway burying two Himachal Road Transport Corporation buses.
A search and rescue operation is on involving local authorities and the Indian Army. The National Disaster Response Force has been summoned.
So far, five people have been rescued.
The disaster spot is some 220 km from the state capital.
According to eyewitnesses, the two buses were stationed at a kiosk located on the highway for refreshments when the disaster occurred.
One of the buses was on its way from Chamba to Manali and the other from Manali to Katra.
The bus from Chamba to Manali was carrying the maximum number of passengers.
Mandi Deputy Commissioner Sandeep Kadam told reporters that the death toll is likely to increase.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)