BEIJING, Aug 27 (Reuters) - The number of people missing in China's Tibet after a Nepal mudslide ‌disaster has risen to 558 including 260 foreign ‌nationals, Chinese state broadcaster CCTV reported on Thursday, as authorities flagged ​more geological risk upstream.

A wall of mud and rock on Wednesday collapsed into a river near Gyirong at the border between the Tibet region and Nepal, triggering a ‌flash flood that killed ⁠scores of people downstream in Nepal, left hundreds missing and washed away houses, roads ⁠and power projects.

China confirmed an official death toll of three on the Tibetan side of the border, CCTV ​reported. Surrounding ​villages within danger zones ​have been evacuated and ‌two villagers have been rescued, it said without elaborating.

Authorities have identified risk from a dammed lake upstream from the Himalayan border crossing that could complicate rescue efforts, CCTV reported.

China's Ministry of Water Resources has increased monitoring ‌and assessment of the lake, ​at the intersection of the Chhochen ​Khola and Purepu Tsangpo ​rivers northeast of the disaster site, to ‌support rescue activity and prevent ​secondary events, CCTV ​reported.

China has also mobilised fire and rescue teams from Beijing and Chengdu to aid local police ​and armed forces ‌in relief efforts, CCTV reported.

(Reporting by Liz Lee, ​Tiffany Le and Beijing newsroom; Editing by ​Muralikumar Anantharaman and Christopher Cushing)