Four South Africans among many missing after catastrophic flash floods in Nepal-Tibet.

Four South Africans are among hundreds of tourists still unaccounted for after devastating flash floods swept through the Nepal-Tibet border region, killing over 90 people and triggering a massive international search and rescue operation.

Nepal's Tourism Board said over 300 travellers remain unaccounted for following Wednesday's flash floods along the Bhote Koshi River, one of the country's most popular trekking and pilgrimage routes.

The missing includes foreign nationals from South Africa, India, the United States, the United Kingdom, Malaysia, the Netherlands and Australia, as well as Nepali citizens linked to nine trekking agencies.

Authorities have cautioned that the figure is preliminary and does not necessarily mean all those listed are confirmed casualties. Many people are believed to be stranded in remote mountain areas without communication, while officials continue verifying who has been safely accounted for.