PHNOM PENH: Pollution in southeast Asia's Mekong River has pushed freshwater dolphins in Cambodia and Laos to the brink of extinction, an international conservation group said yesterday.

The World Wide Fund for Nature (WWF) said only 64 to 76 Irrawaddy dolphins remain in the Mekong after toxic levels of pesticides, mercury and other pollutants were found in more than 50 calves who have died since 2003.

"These pollutants are widely distributed in the environment and so the source of this pollution may involve several countries through which the Mekong River flows," said WWF veterinary surgeon Verne Dove in a press statement.