A giant panda cub, who is a star attraction at Washington's zoo, is recovering after bowel surgery to remove a "lemon-sized mass of bamboo".

Zoo officials say one-year-old Bei Bei is now stable and the "prognosis is very good".

The emergency surgery was required after an ultrasound revealed a blockage "at the top of the small intestine".

Bei Bei earlier showed signs of stomach discomfort and nausea, and was sleeping more than normal and not eating.

"I'm extremely proud and thankful for our team of keepers, veterinarians, animal care staff, volunteer medical experts and all staff who have helped facilitate the urgent response," said Dennis Kelly, director at the Smithsonian National Zoo in Washington DC.

"Bei Bei's prognosis is very good. The challenge will be for our team to monitor him safely and that requires his co-operation."

The giant panda cub will be given water overnight and later will be "transitioned" to soft foods such as sweet potatoes and pears, the officials say.

Bei Bei was born on 22 August 2015. People around the globe monitored his mother's pregnancy on the zoo's "panda cam".

The name - which means "precious" - was chosen by the first ladies of the US and China, Michelle Obama and Peng Liyuan.