Three Germans are among those missing following Wednesday's devastating flash flood in the Himalayan border region between Nepal and China, Chinese authorities said on Sunday.

In Tibet, the death toll stands at 16 while another 546 are missing, Chinese state media reported, citing the regional government.

Among the missing are 261 foreign nationals from 23 countries, including Germany, France, Finland, Portugal and Spain, state broadcaster CCTV reported.

Chinese authorities had notified the relevant embassies and consulates in China, the report said.

The Nepal Tourism Board has said eight Germans are missing. It is unclear if the three German nationals reported as missing by Chinese authorities are included in the figure reported by Nepal.

The Foreign Office in Berlin has said a "a high single-digit number of German nationals" are missing in the area.

Experts have said a glacier collapse in Nepal may have triggered the disaster, sending huge volumes of water down a river valley. In Nepal, 675 people have been reported dead with more than 2,400 others missing.