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Following a tip-off, they found about 750 dogs packed into cages on a truck which were about to be loaded onto a ferry on the Mekong river in Nakhon Phanom province, said Captain Theerakiart Thong-aram.

One man was arrested but several others ran away when the authorities swooped, Theerakiart told AFP.

"Dogs are the third-biggest smuggling problem along the river after timber and drugs," he said.

In August, Thai authorities rescued more than 1,000 dogs that were found stuffed into tiny cages, also being smuggled out of the country to be cooked and eaten in Vietnam.