Giant panda cub a boy, fathered by Smithsonian National Zoo's resident male Tian Tian

The US National Zoo's surviving giant panda cub is a boy and was fathered by the zoo's male giant panda, the zoo has said.

The cub was born on Saturday to panda mother Mei Xiang, who is a top tourist draw in the US capital.

A fraternal twin died on Wednesday of pneumonia likely caused by inhaling food, the zoo said.

The surviving cub is healthy, putting on weight and crying when Mei Xiang tries to leave its den.

Our giant panda cub is male & sired by Tian Tian!

The twins' birth captured international attention, since giant pandas are among the world's most endangered species.

Mei Xiang was artificially inseminated in April using sperm from giant male panda Tian Tian, and also from Hui Hui, a panda in China.

But Tian Tian was identified as the successful father using gene sequencing.

It weighed 157 grams early on Friday, a 16 per cent gain in about 42 hours, officials said.

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