Chinese President Xi Jinping on Wednesday ordered all-out efforts to search for and rescue people missing after devastating flash floods swept through villages and towns near the China-Nepal border in Tibet, causing heavy casualties, Chinese official media reported.

A sudden, massive flood also swept through two central Nepal districts bordering Tibet, killing at least four people, causing extensive devastation at settlements along the river and damaging at least a dozen hydropower projects early Wednesday.

At least 105 Indians and 37 NRIs are among the nearly 400 persons missing, according to the report.

A total of 145 officers and soldiers from the Xigaze detachment of the People's Armed Police have been sent to the affected border port to assist with emergency response operations. Xi called for efforts to evacuate residents at risk.

Drone footage showed some buildings at the port buried by debris, Chinese official media reported.