Maputo (AFP) - Mozambican police said Wednesday four officials had been arrested after 50 kilograms (110 pounds) of rhino horn were stolen from a huge cache seized from poachers only two weeks ago.

The country's largest ever find of illegal wildlife products was uncovered in a villa on the outskirts of the capital Maputo and then stored under armed guard.

It was the equivalent of about 200 dead elephants and rhino, and had a reported street value of about $6.3 million.

But police admitted some of the cache had been pilfered and replaced by fake horns.

"Twelve horns, which amounts to 50kg, were stolen last Friday," police spokesman Emidio Mabunda told AFP.

Six people have been arrested, including four government employees, he said.

The case highlighted the involvement of police and state officials in the organised crime networks driving the rampant poaching across the region.

The US-based Wildlife Conservation Society said this week poachers have killed nearly half of Mozambique's elephants for their ivory in the past five years.

Rhinos -- thought to be extinct in Mozambique -- are frequently targeted by hunters who slip across the border into neighbouring South Africa.

"It deprives me of sleep when policemen are caught within gangs trafficking rhinoceros horns and elephant tusks," Mozambican president Filipe Nyussi said last week at a police event.