The twin giant panda cubs at PairiDaiza zoo clearly had no idea why, when their keepers carried them out into their yard on Thursday, they were greeted with the clicks of dozens of cameras.

The youngsters, which were born at the zoo 60 kilometers from Brussels on Aug 8, could not have known they will be turning 100 days old on Saturday and that the milestone is traditionally one in which pandas get their names.

In this case, their new monikers were picked in a public vote in which 73,000 people took part.

Henceforth, the male panda will be known as Bao Di and his sister will be called Bao Mei. The names mean little brother and little sister and refer to their relationship with another of the zoo's giant pandas, Tian Bao, a male who was born in 2016.

Their parents, Hao Hao and Xing Hui, are on a 15-year loan to the zoo.

Their home, the giant panda garden at PairiDaiza, was inaugurated by President Xi Jinping and his wife Peng Liyuan along with Belgium's King Philippe and Queen Mathilde on March 30, 2014.

In October, Xi and Philippe exchanged congratulatory messages about the pandas' birth in which Xi said that the birth of two cubs deserves joint celebrations. He added that he was confident they would become a beautiful new part of the China-Belgium friendship.

PairiDaiza is the only European animal park to house five giant pandas and Eric Domb, president and founder of the zoo, said at Thursday's naming ceremony: "The fact that the cubs are in good health means that the relationship between Belgium and China is excellent. The cubs are a symbol for the relationship."

He said the success would not have been possible without the support of China.

Li Guo, an expert from the China Conservation and Research Center for Giant Panda, has been working closely with his Belgian colleagues and said: "There has been a lot of work these past three months, since the birth. It's a very special 100 days, a time for celebration."

He said his work at the zoo is almost over and that he will soon return to China.

The cubs now weigh 5.5 kilograms each, in stark contrast to the 150 grams that Bao Mei was at birth and the 160 grams Bao Di initially weighed.

"I sincerely hope the giant pandas will become ambassadors to help the Belgian public better understand China," said Cao Zhongming, China's ambassador to Belgium.

The public will not get to see the pandas for another month though, because the zoo is closed for the winter season. It will reopen for Christmas between Dec 14 and Jan 5.