South Africa's Kruger National Park is recruiting retired game rangers to replace its striking ranger force, a spokesman said Tuesday, amid a rhino poaching crisis that has hit record scale.

The world-famous safari destination's 181 rangers launched an open-ended strike Friday with other conservation staff.

"We cannot leave those areas unmanned," Kruger spokesman William Mabasa told AFP.

He said soldiers and police had been dispatched to fill in for the striking rangers and that the park had not seen an increase in poaching so far.

But he added: "We do not know whether those structures (military and police reinforcements) will be here forever. We have to make a plan in case they withdraw."

The strike comes as Kruger battles a spike in poaching driven by booming demand for rhino horn on the Asian black market.

More than half the record 450 rhinos killed across South Africa last year were from Kruger, according to authorities.

The largest horns can fetch up to half a million dollars and feed the Asian traditional medicine market, despite scientific evidence that they have no medicinal value. They are made of the same substance as human fingernails.