Workers at a zoo in Cincinnati, Ohio, have shot and killed an endangered gorilla after a four-year-old boy fell into its enclosure, officials have said.

The child is believed to have crawled through a public barrier into the Gorilla World enclosure at Cincinnati Zoo & Botanical Garden on Saturday afternoon, and tumbled into the exhibit’s moat.

Zoo director Thane Maynard said the lowland gorilla – a 17-year-old male named Harambe weighing around 180kg – “went down and got him”.

Witnesses said the gorilla dragged the boy around the enclosure for around 10 minutes before the zoo’s response team shot and killed the primate, local media reported.

Gorilla and boy in enclosure

The boy in the enclosure with the gorilla. Pic: WLWT

The child was taken to hospital with injuries that were not life-threatening, media quoted the police as saying.

The zoo’s dangerous animal response team decided to shoot rather than tranquilise the gorilla because a tranquiliser would not have taken effect immediately, Mr Maynard said.

Pic: Tangie J Hollifield/Facebook

The child was later treated in hospital. Pic: Tangie J Hollifield/Facebook

He said the gorilla did not appear to be attacking the child, but that it was “an extremely strong” animal in an agitated situation.

“It seemed by our own dangerous animals response team to be a life-threatening situation. They saved that little boy’s life,” Mr Maynard said.

“We are all devastated that this tragic accident resulted in the death of a critically-endangered gorilla.

“This is a huge loss for the zoo family and the gorilla population worldwide.”

The zoo, which houses 11 gorillas, prides itself for its work in protecting endangered species.

It has been part of successful captive breeding efforts in recent years in the effort to save the endangered Sumatran rhino.