The deadly flood in Nepal's Bhote Koshi River that killed at least nine people and left more than two dozen missing this week was triggered by the draining of a supraglacial lake in the Tibet region of China, a regional climate monitoring body said on Wednesday.

At least 19 people, including six Chinese workers at the Beijing-aided Inland Container Depot, remain missing in Nepal after Tuesday's floods that also washed away the "Friendship Bridge" that links Nepal and China.

China's official Xinhua news agency has said 11 people were unaccounted for on the Chinese side of the mountainous border region.