Laos has denied it is pushing forward with the controversial Xayaburi hydropower dam in violation of international legal obligations, the country’s state media reported on Friday.

Conservation groups have said photos and interviews with villagers clearly demonstrate that Thai firm Ch.Karnchang Public Company Ltd is engaged in much more than “preparatory” works as Laos has claimed.

Laos Deputy Minister of Energy and Mines Viraphonh Viravong told the Vientiane Times daily that only “sub-surface surveying” had commenced on the project, not dredging of the river bank as claimed by the group International Rivers.

“We plan to invite development partners and Mekong River Commission member countries to visit the project site so they can see the actual development for themselves,” he said.

Te Navuth, secretary-general of the Cambodian National Mekong Committee, said it was plain to see the company had begun work that went beyond exploration, including dredging.

“I don’t want to argue about this; they always say something else, but we can see,” he said.

Navuth said Laos should join a study on the downstream impact dams on the mainstream Mekong river that Cambodia and Vietnam agreed to conduct in a Memorandum of Understanding signed on Tuesday.

The governments agreed to a large-scale study of the impact upstream dams have on the lower Mekong river basin, including the Tonle Sap river system and the Mekong Delta.

Ame Trandem, Southeast Asia program director of International Rivers, said the study would take three years and could not save the Mekong from serious damage if construction on the Xayaburi continued.

“What needs to happen now is that Thailand and their company Ch.Karnchang ... need to agree with the government of Laos to stop construction of the Xayaburi,” she said.

Under a 1995 agreement with Cambodia, Vietnam and Thailand, Laos was obligated to not begin construction without a prior notification and prior consultation agreement between the four countries, which has not been completed.

“If Laos decides to go ahead with Xayaburi, it would be violating this agreement and thereby violating international law,” she said.

To contact the reporter on this story: David Boyle

With assistance from Reuters