South Africa may impose new limits on trophy hunts as it combats a devastating surge in rhino poaching, with 150 killed illegally so far this year, the environment ministry said Thursday.

Big game hunters are allowed to kill a limited number of rhinos every year, with their horns exported as mounted trophies.

But a Thai man was arrested this week and accused of manipulating the system, making bogus trophy hunts to feed the demand for rhino horns in the Asian traditional medicine market.

His was the fourth arrest in an alleged syndicate that hired Thai strippers and prostitutes to pose as hunters and export the horns.

The ministry "will pursue a halt to the issuance of hunting permits to hunters coming from countries that do not have appropriate legislation to monitor whether the trophy is used for the purpose as reflected on the permits," it said in a statement.

The ministry is also in talks with Vietnam's agriculture department on how the countries can work together to address the matter of hunting permits and ways to stop possible abuses.

South Africa has also asked Vietnam "if they could conduct inspections and verify that the white rhinoceros trophies exported from South Africa to Vietnam are still in the possession of the hunters," the statement said.

The animals' distinctive horns are hacked off to be smuggled to the lucrative Asian black market, where the fingernail-like substance is falsely believed to have powerful healing properties.