Thai customs police on Thursday unveiled a massive three-tonne cache of seized pangolin scales intended for Asia's lucrative wildlife markets, where feverish demand for the "scaly anteater" has turned it into the most trafficked mammal on earth.

The shy pangolin's brown scales are made of nothing more than keratin -- the same substance as fingernails -- but are highly prized in Vietnam and China where they are misleadingly touted as bearing medicinal properties.

Soaring demand for the products has seen an estimated one million pangolins plucked from Asian and African forests over the past decade, shunting them onto the list of species at the highest risk of extinction.

On Thursday, Thai police revealed nearly three tonnes of pangolin scales, packed into white bags, that had been seized from two air cargo hauls at Bangkok's main airport.

The contraband was shipped from the Congo, smuggled through Turkey and eventually bound for Laos -- a key transit hub for regional trafficking syndicates.

"This is the biggest lot (of pangolin scales) that we have seized," Police Major General Worapong Thongpaiboon, acting commander of the Natural Resources and Environment Crime Division, told AFP.

Endangered pangolins John SAEKI, Laurence CHU, AFP

Thailand's CITES director said the final destination was almost certainly intended to be China or Vietnam, where the price of pangolin scales runs around $1,700 per kilo.

"After (customers) clean and dry the scales they fry and mix them with traditional medicine that they believe cure cancer and enhance sexual performance," Somkiat Soontonpitakkool told AFP.

There is no peer-reviewed scientific evidence to support any medicinal properties for pangolin scales.

Steve Galster, executive director of the anti-trafficking group Freeland, applauded the police's work but stressed that it fit a familiar pattern: the products were confiscated but the criminals behind the trade remain at large.

"With wildlife crime they seize, check the box and move on," he said.

"Wildlife crime is still not high-level for most governments. They're not told from the top level to focus on this, so usually it's good enough just to do a seizure. That's the problem," he added.