The massive snow slide happened around 9 a.m. local time and covered up two climbing camps on Manaslu Mountain in the district of Gorkha, Nepalnews.com said.
Police said the nine known victims were tourists from France and Germany, but their identities weren't released.
Three helicopters were deployed in the rescue operation at an altitude of more than 20,000 feet, the report said.
Crews were able to rescue 12 people from the camps, police said.
There was no immediate indication if further slides were likely.