OHIO • Workers at the Cincinnati Zoo in the American state of Ohio shot and killed a gorilla after a four-year-old boy fell into its enclosure, officials said.

The boy crawled through a barrier into the enclosure and fell about 3.7m into a moat surrounding the habitat last Saturday, zoo director Thane Maynard told reporters. The gorilla, a 17-year-old male named Harambe which weighed more than 180kg, grabbed the boy and dragged him around the habitat.

The zoo's dangerous animal response team shot and killed the gorilla around 10 minutes after the boy entered the enclosure.

Mr Maynard said the team decided to shoot the gorilla rather than tranquillise it because a tranquilliser would not have taken effect immediately.

"It seemed by our own dangerous animal response team to be a life-threatening situation. They saved that little boy's life."

The boy was hospitalised with injuries that were not life-threatening, the media quoted the police as saying. In a statement, the zoo said the boy was alert when taken to a hospital.

The zoo houses 11 gorillas, according to its website. "We've never had a situation like this," Mr Maynard said.

Two female gorillas were also in the enclosure at the time of the incident.

Harambe, a western lowland gorilla, was born at the Gladys Porter Zoo in Brownsville, Texas, and was moved to the Cincinnati Zoo in 2014.

Western lowland gorillas, which live in remote rainforests in Africa, are classified as a critically endangered species, according to the World Wide Fund for Nature.

Mr Maynard said the zoo had hoped to use Harambe for breeding.

The zoo employees were devastated at losing the rare primate, he added. "This is a huge loss for the zoo family and the gorilla population worldwide."

Earlier this month, a zoo in Chile's capital said it was forced to kill two lions to protect a suicidal man who had entered their cage in front of horrified visitors.

Security protocols kicked in immediately when staff saw the man climb down with a rope into the African lions' enclosure, Ms Alejandra Montalva, head of the Santiago Zoo, told television network TVN.

The carnivorous felines, a male and a female, had attacked the man instinctively, so they had to be put down.

Ms Montalva said anaesthetic darts would not have stopped the attack in time.

"We're shaken by this because the animals in the zoo are part of our family," she said.

"These were lions that had been with us for more than 20 years."

The man, in his 20s or 30s, was taken to a hospital with critical injuries.

REUTERS, AGENCE FRANCE-PRESSE