Poachers "wiped out" the entire elephant herd in Sierra Leone's only wildlife park, wildlife managers said after police said they had arrested a gang of 10 poachers.

"It is likely that the elephant population is wiped out," Ibrahim Bangura, senior superintendent of the agriculture ministry's Conservation and Wildlife Management Unit.

The six elephants were shot and "crudely butchered, their bodies slashed with sword marks and their tusks virtually wrenched from their skins," said Bangura.

Police said 10 poachers were arrested after the discovery of the elephant carcasses and those of four buffaloes in Outamba Kilimni national park, near the border with Guinea.

The men, from Sierra Leone and Guinea, are being held in the northern town of Koinadugu.

"We believe the killing was done between September and October and this is a great blow to all of us," said Bangura.

"We had treasured the elephant population in the park as they are very important to the development of ecotourism in the country."

Tourism Ministry officials said a crack military unit has been stationed near the park after frequent incursions by poachers from Guinea and Mali hunting wild animals.