BANGKOK: Hundreds of people are missing and an unknown number believed dead after the collapse of a hydropower dam in southeast Laos, state media reported Tuesday.

The accident happened at a dam in southeastern Attapeu province late Monday, releasing five billion cubic metres of water with "several human lives claimed, and several hundreds of people missing," Laos News Agency said.

The dam is being built by Xe Pien-Xe Namnoy Power Company, or PNPC.