South African police say they have arrested a Thai man who organized rhinoceros hunts as part of a scheme to sell their horns on the black market.

Suspect Chumlong Lemtongthai was due to appear in court early this week.

He was arrested at his Johannesburg-area home on Saturday, after a year-long investigation by the South African Revenue Service.

Officials allege he obtained rhino hunting permits meant to be used for legal trophy hunting. Authorities say he then organized hunting trips intended to secure the rhino horns.

Authorities say Lemtongthai bought the horns from the hunters for about $9,500 per kilogram. Rhino horns are now worth more than gold.

The rhino horns are ground up and used in traditional medicines or as aphrodisiacs, particularly in Southeast Asia.

Authorities says there has been an upsurge in poaching by organized crime syndicates using sophisticated and high-tech weapons to get the valuable horns.

The Switzerland-based International Union for Conservation of Nature says more than 90 percent of the world's rhino population is in South Africa.

The group has warned the number of rhinos could decline unless the rapid increase in poaching is stopped.