Chimpanzees at a sanctuary in South Africa have left a man seriously injured with bite wounds after pulling him into their enclosure.

The man, described as a ranger, was leading a tour group at the Jane Goodall Institute Chimpanzee Eden yesterday.

Two chimpanzees grabbed his feet and pulled him under a fence into their enclosure, said Jeffrey Wicks of the Netcare911 medical emergency services company.

The man had "multiple and severe bite wounds" and was dragged nearly a kilometre by the chimpanzees.

Local media reported the man was an American researcher.

The international institute founded by primatologist Jane Goodall opened the sanctuary in 2005.

It is a home to chimpanzees rescued from further north in Africa, where they are hunted for their meat or held captive as pets.

Beeld, a South African newspaper, reported that the man was an American researcher who was giving tourists a lecture at the time of the attack.

The tourists were escorted to safety by staff members as the chimpanzees dragged the man out of their enclosure.

The sanctuary's director fired into the air to scare the chimps away from the man, and then chased the animals back into their enclosure. The man reportedly lost part of an ear and parts of his fingers.

In the United States this week, lawyers for a Connecticut woman severely disfigured in 2009 when she was attacked by a friend's pet chimpanzee, filed papers accusing state officials of failing to seize the animal before the mauling despite a staff member's warning that it was dangerous.

Mediclinic Nelspruit, the hospital where he was taken, said he was in intensive care in critical condition after undergoing surgery.