Thai airport officials linked to rhino trade

The horn was brought into Suvarnabhumi Airport in January by Vietnamese migrant workers paid $500 per trip, said Narasak Hemnithi, commander of the Natural Resources Environmental Crime Division.

"After arriving in Bangkok they were asked to put the rhino horn on a trolley and leave it somewhere nobody could see and then police would come and collect it," he told AFP.

"We have evidence, especially closed circuit television footage," he added.

In early January a Vietnamese man was arrested after leaving rhino horn worth more than half a million dollars in unattended luggage at Suvarnabhumi.

Illegal hunting of rhinos has risen in recent years to meet surging demand for their horns in parts of Asia, in particular Vietnam where they are highly prized for their supposed medicinal qualities.

A record 668 South African rhinos were slaughtered for their horns in 2012, an increase of nearly 50 percent compared with 2011, according to conservation group WWF.

Their plight is one of the issues topping the agenda at a major conference on endangered species in Bangkok this week, with wildlife groups urging Thailand to step up efforts to crack down on trade in ivory and rhino horn.