A huge wall of mud and rock collapsed into a river on the Himalayan border of Nepal and China's Tibet on Wednesday, triggering catastrophic flooding on the Nepali side that killed at least 95 people and left hundreds of tourists missing.

In a still-unfolding disaster, verified videos showed dozens of people swept away at the border, with authorities on both sides fearing far higher casualties and massive destruction.

Houses, roads and power projects were swept away in Nepal, while officials in Tibet said they feared "major casualties", with some people missing in the county of Gyirong after a mudslide hit a border land crossing.

Initial reports suggested an earthquake in the area could have triggered an avalanche and caused the floods, Nepal's foreign minister, Shisir Khanal, told the country's parliament on Wednesday, local media reported.