Vietnam was the "top destination for rhino horn," creating a poaching crisis in South Africa, said the report, which identified 23 countries "facing high levels of poach and trafficking" in horns, ivory and animal parts.
Laos and Mozambique were cited as having failed on ivory trade compliance and enforcement, the BBC reported.
Vietnam, the report found, failed on "key aspects of compliance and enforcement" for the rhino and the tiger-part trades.
"It is time for Vietnam to face the fact that its illegal consumption of rhino horn is driving the widespread poaching of endangered rhinos in Africa, and that it must crack down on the illegal rhino horn trade," Elisabeth McLellan, WWF Global Species Program manager, said in a statement.
The wildlife group commended progress made in some countries.
"There were important advances in compliance in 2010-2012, with introduction of stricter legislation, wildlife trade controls and penalties in a number of countries, including China, India, Laos, Malaysia, Nigeria, Russia, South Africa and Zimbabwe," it said.
However, it noted, "major prosecutions for wildlife crime are still rare."
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