Thousands of thankful, sobbing fans flocked to a Tokyo zoo Saturday to bid an emotional farewell to a pair of beloved pandas before their imminent return to China.

Sporting T-shirts, hats and sun umbrellas featuring the black and white bears, visitors shed tears, took selfies and eagerly waved at Ri Ri and Shin Shin on the panda couple's penultimate day at Tokyo's Ueno Zoological Gardens. 

More than 2,000 panda lovers formed long queues outside the zoo Saturday morning, some having spent the whole night there armed with picnic blankets and camping chairs.

Among the most committed was Mayuko Sumida, 44, who said she had arrived around 10 pm the previous night, carrying with her panda-shaped key rings.

"I'm overwhelmed," she said after admiring the two for the last time.

"They are the best duo that brings comfort and smiles to me."

The mammals are immensely popular around the world, and China loans them out as part of a "panda diplomacy" program to foster foreign ties.

The pandas Ri Ri and Shin Shin arrived at Ueno Zoo in 2011 and were due to stay until February 2026, but Japan and China agreed it would be better for the 19-year-olds to return to their home country in light of their declining health.

They will be transported back to China on Sunday. 

'Emotional support' pandas

On Saturday, strict crowd control measures were in place at the zoo to escort fans away after giving them just a few minutes to adore and photograph the pair through the glass.

Ri Ri and Shin Shin were "like the sun to me" and "always gave me emotional support", Machiko Seki, who like other fans wore black to avoid window reflections ruining their pictures, told AFP.

"When I look at their smiles, whatever worries me just goes away... I can't be more grateful for them," the woman in her 50s said, shedding tears.

The pair gave birth in 2017 to cub Xiang Xiang -- the zoo's first baby panda since 1988, who became a massive draw -- as well as twins in 2021.

Many fans cried when Xiang Xiang was returned to China last year, and her departure was broadcast live on local television.

Michiyo Matoba, 61, has been coming to see Xiang Xiang's parents almost every week.

"Ri Ri loves climbing trees so I hope he will enjoy those mountains of China as much as he likes, and the glutton Shin Shin will hopefully start eating to her heart's content after regaining her health", she said.

Despite the panda diplomacy, relations between the two countries have soured in recent years following Beijing's growing maritime assertiveness.

Politics, Matoba said, doesn't taint her love for the animals.

"Just like pandas, I hope Japan and China can be friends," she said.

There are an estimated 1,860 giant pandas left in the wild, mainly in bamboo forests in the mountains of China, according to environmental group WWF.

There are about 600 in captivity in panda centers, zoos and wildlife parks around the world.