TEHRAN (Press Shia Agency) – A hydropower dam unleashed 5 billion liters of water after it collapsed in Laos, leaving several people dead and hundreds of others missing.

The Xepian-Xe Nam Noy collapse sparked flash floods in six villages in the Attapeu province late last night, according to the Laos News Agency.

"Several lives were lost", "hundreds of people are missing" and more than 6,000 have been made homeless, it added, the Sun reported.

Officials brought in boats to help evacuate locals in the San Sai district after water levels suddenly rose, ABC Laos news reported.

It is unclear what caused the collapse but environmental groups have raised concerns about Laos' hydropower ambitions for years.

Their fears included the negative impact the dams had on the Mekong River, its flora and fauna and the rural communities which depend on it.

Local authorities are pleading with the government to provide immediate emergency aid including food, water, clothing and medicine.

Laos, one of Asia's poorest and most secretive countries, has plans to become the "battery of Asia" by selling power to its neighbors through a series of hydropower dams.

The £915m dam was being built by the Xe Pian-Xe Namnoy Power Company (PNPC).

A number of other companies including Thailand's Ratchaburi Electricity Generating Holding, South Korea's Korea Western Power and state-run Lao Holding State Enterprise were also involved.

The 410 megawatt capacity dam was meant to begin commercial operations by 2019, according to the venture's website.