(CNN) A British zoo has announced the birth of two Amur leopards -- believed to be the world's rarest big cat.

Twycross Zoo , in Leicestershire, central England, has released the first images of the as yet unnamed five-week-old cubs.

The animals have begun venturing outside their den, and visitors can now catch a glimpse of them on a live-stream shown on a big screen outside the leopards' enclosure.

Amur leopard Kristen watches as one of her cubs explores their enclosure.

Native to the forests and mountains of Russia's far east, Amur leopards are a critically endangered species. They are on the brink of extinction in the wild, under threat from habitat loss and poachers hunting them for their fur.

There are thought to be less than 70 leopards left in the wild, with 200 more living in zoos across the world.

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