Two Amur leopards - believed to be the world's rarest big cat - have been born at Twycross Zoo in Leicestershire.

The cubs, who are as yet unnamed, are just a few weeks old and only recently ventured out of their den.

There are only about 200 Amur leopards in the world, which are mostly in captivity, the zoo said.

The cubs' parents, Kristen and Davidoff, also produced two cubs in 2014, making them a "real asset" to the worldwide breeding programme, a spokesman added.