A jaguar clawed a US woman who climbed over a barrier to take a picture at the Wildlife World Zoo near Phoenix, Arizona, officials said.
Smartphone video of the incident showed at least one gash on the woman's left forearm as she writhed on the ground in pain on Saturday.
"I hear this young girl screaming: 'Help, help, help' ... and the jaguar has clasped its claws outside the cage around her hand and into her flesh," witness Adam Wilkerson told Fox 10 television.
Wilkerson's mother distracted the jaguar by pushing a water bottle through the cage, and Wilkerson said he pulled the woman away.
Video later showed the animal chewing on a plastic water bottle.
The identity of the woman, in her 30s, was being withheld, said Shawn Gilleland, a spokesman for Rural Metro Fire, the agency that responded to the incident.
She was taken to a hospital and treated, then later returned to the zoo to apologise, Gilleland said.
"She wanted to take a selfie or a picture of the animal, and she put her arm close enough to the cage that the cat was able to reach her," Gilleland said.
The zoo's statement said the female jaguar never left its enclosure, and that the incident was being fully investigated.
"We can promise you nothing will happen to our jaguar," the zoo said on Twitter, responding to public concerns the animal might be put down.
The barrier surrounds the entire exhibit, creating a buffer of several feet (metres) from the enclosure, zoo spokeswoman Kristy Morcom told Fox 10.
"There is climbing involved. It's not something that is easily done," Morcom said. "These are wild animals and those barriers are put there for a reason."