An American man has been left badly injured in hospital after being attacked by two chimpanzees at a sanctuary in eastern South Africa.
According to medical staff and local media, he was dragged under a perimeter fence on Thursday and pulled through the enclosure for nearly a kilometre.
He suffered severe bite wounds and is now in a stable condition in intensive care, Associated Press reported.
The Jane Goodall Institute Chimp Eden houses rescued chimps.
After the incident, its executive director said staff were investigating what had caused the chimps to attack.
'Severe bite wounds'
In an interview with The Telegraph newspaper, David Oosthuizen said: "We understand that the gentleman is stable and we really feel for him. This has been very upsetting for everyone - it is just horrific."
He told the newspaper that because of the abuse suffered by the animals before they were rescued, staff at the reserve were cautious around them and mindful of their greater strength.
Jeffrey Wicks, a spokesperson for the Netcare 911 private ambulance company in South Africa, said the man who was attacked had been leading a tour group at the reserve when two chimps grabbed his feet and pulled him under a fence into their enclosure.
He said the victim has suffered "multiple and severe bite wounds".
Paramedics reportedly needed an armed guard to reach the man in the chimpanzee enclosure, which is located within a nature reserve.
The international institute was founded by renowned primatologist Jane Goodall in 2006 to house chimpanzees rescued from central Africa.
Although they share much of their biology with humans, chimps have been known to attack unexpectedly.
In the United States this week, lawyers for a woman severely disfigured in 2009 when she was attacked by a friend's pet chimpanzee filed papers accusing state officials of failing to act on warnings that it could be dangerous.