File picture: Xinhua.

London - A rare snow leopard has died at a British zoo after keepers shot the animal following its exit from an enclosure that had been left open, the zoo said on Friday.

Eight-year-old male snow leopard "Margaash" died after walking out of its enclosure one day last month around dusk, after the zoo had closed and no visitors were present, Dudley Zoo, in the English West Midlands, said in a statement.

The zoo said keepers believed they had "no other option in the interest of public safety" than to shoot the animal, reasoning that a tranquilizer dart would take too long to subdue it.

The door to the enclosure had been "left open through keeper error, which has resulted in a disciplinary investigation of those involved," the zoo said.

"This was an incredibly sad incident and our staff are understandably heartbroken," Zoo Director Derek Grove said.

"Efforts to persuade Margaash to return to his enclosure failed and as the animal was close to surrounding woodland and dark was approaching, the vet did not believe a tranquilizer dart was a safe option due to the amount of time the drug takes to work," Grove said.

Margaash, born in captivity at another British zoo in 2010, had lived at Dudley Zoo with three-year-old female snow leopard "Taiga."

Scientists estimate that between 3,920 and 6,390 snow leopards remain in the wild, according to the Snow Leopard Trust. Most of them live in remote, high-altitude areas of western China, Mongolia and other parts of Central Asia.