The landslide, triggered by heavy rains, hit Sindhupalchowk district on Saturday after the Sunkoshi river, which flows across the border into Bihar as the Kosi river, was blocked creating an artificial lake near Nepal-Tibet border.
Chief District Officer Gopal Parajuli confirmed that all 123 missing in the landslide were dead on the basis of data submitted by local people.
"The missing persons were declared dead after the nature of the site showed no possibilities of finding the bodies," said Parajul. He said rescue work has been called off for the time being as the deployment of heavy machinery and earth pullers may trigger more landslides.
Earlier, 33 were pulled out from the rubble laid bare by Nepal's worst landslide in over a decade. Police and army personnel carried out search and rescue operations for the past five days to locate the missing persons.
They drained out water from the artificial lake using controlled explosions. About 5,000 people across 11 districts have been affected due to the landslide; more than 1,000 have been displaced. Over 60 houses in three villages were swept away and dozens of other structures damaged.
The government has distributed Rs 40,000 as relief to the families of dead and missing in the disaster. Those whose houses were damaged were given Rs 5,000. Eighteen people were rescued by Nepal Army.
The district has been evacuated and some 600 stranded tourists, including Indian nationals, have been moved to safer locations. In July 2002, over 150 people were killed when multiple mudslides struck two villages in the eastern district of Khotang.