A game ranger with a rifle slung across his shoulders follows a bush trail through South Africa's Kruger National Park, alert to the slightest sound or movement.

He faces threats not only from lions and elephants but humans as well - heavily-armed poachers who stalk the park day and night.

Rhinos are their usual prey, and they have killed 380 this year. But in an ominous sign of more trouble ahead, the park announced on Thursday that an elephant had been killed for its tusks in the second incident to involve the large animals.

The vast park had been free of elephant poaching for more than a decade before the first one was shot and had its tusks hacked off in May.

Elephant tusks and rhino horns can fetch high prices, especially in Asia, and poachers are ready to go to war to get them.

"Our lives are also at risk, because we stand in the way of what the poachers want," said veteran ranger Stephen Midzi. "They are prepared to kill, and some are armed with AK-47 rifles."

Midzi is one of nearly 350 rangers who traverse the 2-million-hectare park on foot, checking for any signs of unusual activity.

"Our primary task is to protect all the animals and the ecosystem of the park, but the rhino is facing the biggest threat," he said. The horns are mistakenly believed to have medicinal properties.

Rhino poaching rose from 13 animals killed in 2007 to the slaughter of 1,004 last year, mostly in the Kruger park.

Midzi leads a team of 16 rangers in charge of 90,000 hectares in the southern section of the park, where he says most rhino poaching occurs.

It's a job that requires alertness at the highest level along with bush survival skills, where every animal trail is inspected to detect the presence of invaders.