Then earlier this month, two white rhino adult males were shot dead and had their horns hacked off by poachers.

South African officials linked up with their counterparts in Mozambique -- which shares a 200 mile border with the Kruger Park -- and tracked the suspects 12 miles into Mozambique to a base where four rhino horns were confiscated.

Six Mozambican men have been arrested by Mozambican police in connection with the poachings.

"Investigation into...other rhino poaching incidents in the same area over the past two years, is likely to lead toward more arrests," South Africa's Environment Ministry said.

South African Environment Minister Valli Moosa said the cross-border cooperation should assuage security fears surrounding the planned creation of the Great Limpopo Transfrontier Park, which will include South Africa's Kruger and reserves in Mozambique and Zimbabwe.

"It is this sort of operation that proves that the Great Limpopo Transfrontier Park will become a sanctuary against poachers for Africa's precious wildlife," Moosa said.

But animal rights activists have questioned the wisdom of tearing down fences along Kruger's border with Mozambique before proper anti-poaching units are set up.

"The fact of the matter is that those animals are dead so there is still a long way to go," said Jason Bell-Leask, the regional director for the International Fund for Animal Welfare.

Rhino horn is prized in many parts of Asia for its supposed medicinal qualities and in the Arab state of Yemen, where it is used to make traditional dagger handles.