Hua Mei needed help in knowing how to breed

Hua Mei was born in the US but moved to China in February.

Officials said they had determined that one of the twins was a boy, but they could not check the other one because Hua Mei was still cuddling it.

The news was cause for celebration at the reserve she lives in, because pandas rarely breed in captivity and are endangered in the wild.

"We are all very excited. The cubs are in good condition," said Li Wei, from the Wolong Panda Conservation Centre in Sichuan, southern China.

Before she became pregnant, Hua Mei had been shown videos as preparation for a series of "blind dates" because experts feared she had little knowledge of mating after living in captivity.

Born to two Chinese pandas on loan to San Diego zoo, Hua Mei is the first foreign-born panda to return to China.

China earlier this year announced the results of a first comprehensive survey of its wild panda population.

This showed there were an estimated 1,600 of the creatures left in the wild, 40% more than previous figures suggested.

Correspondents warned that the numbers might reflect the fact that the survey was so thorough, rather than a genuine recovery in numbers.