Doctors are reporting improvement in the condition of an American graduate student attacked by chimps he was studying in South Africa.

In a statement, Mediclinic Nelspruit said Andrew F. Oberle, who had been in critical condition since Thursday's attack, was stable enough Sunday for doctors to bring him into the operating room to clean and stitch his multiple bites and attend to fractures and other injuries.

Oberle remains in intensive care, but is no longer in critical condition.

Two chimpanzees at the Jane Goodall Institute Chimpanzee Eden in eastern South Africa pulled Oberle under a fence into their enclosure.

Oberle, 26, is studying anthropology at the University of Texas at San Antonio. He was on his second study visit to the sanctuary for abused and orphaned chimpanzees.