Surveillance footage posted on Chinese social media shows a wall of mud and debris rushing towards the port, with people running as parked vehicles were surrounded by floodwater.
Chinese state broadcaster CCTV said the disaster on the Nepalese side had caused major casualties and left people missing at the port. The footage, which was later removed from Chinese platforms, was verified by AFP using satellite and street-view data.
The flooding came as rescue teams searched across Nepal and Tibet after a disaster along the border. On 27 August, Nepalese authorities said at least 270 people had died and 823 remained unaccounted for, including 517 foreign tourists. On the Chinese side, state media reported three deaths and 558 people missing at Gyirong, including 260 foreigners.
The US Geological Survey said the disaster was caused by a glacial collapse that triggered a huge debris flow, rather than the magnitude 4.4 earthquake initially reported. Nearly 800 Chinese emergency workers were deployed in Tibet, while authorities warned that further flooding remained possible.