Britain's Prince William on Thursday warned that vulnerable species are being killed at a "horrifying" rate, as he addressed a wildlife conference in Vietnam -- a country criticised for failing to curb the illicit animal product trade.

With its growing class of wealthy elites, Vietnam has become a main market for rhino horn and ivory and a key transit route for the smuggling of illegal wildlife products from Africa to other Asian countries, notably China.

William, a conservation champion, urged governments around the world to act to save vulnerable species before it is too late.

"We know that we aren't moving fast enough to keep up with the crisis. Rhinos, elephants, pangolins, lions, they are still being killed in horrifying numbers," he said at the Hanoi Conference on Illegal Wildlife Trade.

"While we've made progress, the truth is we are still falling behind. A betting man would still bet on extinction."

The prince cautioned that poachers and trafficking syndicates are becoming more sophisticated and said appetites for wildlife products such as ivory and rhino horn need to be stamped out.

The global illegal wildlife industry, worth an estimated $20 billion, is driven chiefly by demand in Vietnam and China for decorations or traditional medicines with little or no proven benefit.

Stricter law enforcement in China in recent years has driven many buyers to Vietnam, which conservation groups have said is failing to punish criminals and enforce the law.

- 'Time bomb' -

Pressure on Vietnam has seen much of the trade move to the web, led by China's popular social media platform WeChat.

"Online they're still operating unimpeded, Facebook, WeChat, there's still a tremendous amount of wildlife being offered for sale," said Wildlife Justice Commission director Olivia Swaak-Goldman.

"We are at a time bomb... if we keep going this way we won't have any more of these iconic species."

In an illustration of the challenges, a WJC investigation Nhi Khe village just 20 kilometres (12 miles) south of Hanoi found a major black market for illegal wildlife products such as tiger skins, rhino horns, ivory and pangolins.

Their year-long probe also uncovered hollowed out rhino feet and baby tiger cub wine for sale, mostly for Chinese tourists.

There were no illegal wildlife products to be found in the village Thursday, with one shopowner telling AFP it has become increasingly difficult to find such items.

"There used to be shops selling ivory, now I don't hear of them anymore. If there are, they must be doing it secretly. It's not easy to buy, you need to be introduced by someone who trusts you," said the man, who runs a trinket shop, declining to provide his name.

Vietnam's vice president earlier echoed Prince William's urgent appeal.

"The illegal wildlife trade on a global scale has increased and become more complicated," said Dang Thi Ngoc Thinh.

"This is a global issue and no single industry, sector or country can effectively combat the problem of illegal wildlife trafficking," she added, urging international cooperation to combat the scourge.

More than 40 countries are represented at the two-day meeting, alongside NGOs and conservation groups, the third held since Britain hosted it in 2014 and Botswana last year.