Five cheetah cubs born last week by caesarean section at a Cincinnati Zoo in the United States are now under critical care in the zoo's nursery.

According to zoo staff the cubs' immune systems have not properly developed.

The cubs are fed every three hours in the hope that they will gain weight and survive.

Cheetahs are endangered. Their population worldwide has shrunk from about 100,000 in 1900 to an estimated 9-12,000 cheetahs today.