The animals were born at Whipsnade Zoo on 25 June, the Zoological Society of London (ZSL) said on Wednesday, to mum Ruby and dad Nilo.

Their sex isn't known and their names will be decided after their first vet visit at eight weeks.

They each weighed just 113g (4oz) at birth, and have not left their nest yet.

Zookeepers, who say the twins are being well cared for by their parents, wondered if mum Ruby was pregnant for the first time and tried to make her comfortable.

Keeper Grant Timberlake said: "We were ecstatic when we spotted her curled up in one of the nesting boxes we had prepared, using her bushy red tail to keep the two cubs warm.

"Ruby has been doing an incredible job feeding and caring for the twins, so we're leaving the family to bond together, only checking in on them when she pops outside to eat."

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Illegal trade, poaching and deforestation, have combined to reduce the wild red panda population to possibly as few as 2,500, the World Wildlife Fund (WWF) estimates.

Two new twins of the species, which originates in the Himalayas and Western China, is internationally significant.

Zookeeper Grant Timberlake said: "These twin cubs give us double hope for the species, as they were born as part of an important European breeding programme for endangered red pandas, designed to keep a backup population safe in conservation zoos - while we tackle the issues they're facing in the wild."