Japan's beloved elderly giant pandas Shin Shin and Ri Ri were safely returned to China on Sunday, Tokyo's Ueno Zoological Garden reported on its website.

The two pandas arrived at the Ueno Zoo in 2011, bringing a little lightness to the country just months after a devastating earthquake and tsunami hit Japan on March 11 of that year and continued to draw fans of all ages over the years.

When it was announced a month ago that the elderly pandas would soon be returned to China for high blood pressure treatment, visitors flocked to see the pair before they left.

Hiyori Sakurai, an artist in her 30s, said she has been visiting the zoo every Sunday and even some weekdays when she could take time off from work.

"Whenever I go through a hard time, I would go see Ri Ri and Shin Shin, and they always cheered me up," she said.

Etsuko Tokuda, a self-employed woman in her 60s, has been going to the zoo almost every day since the return announcement.

"Each day was important to me. I wanted to see them even if they were sleeping."

Native to China, pandas have, through the years, become "envoys of friendship," and China's offer of pandas to other countries has been dubbed panda diplomacy.

Saturday was the last chance to see Shin Shin and Ri Ri at the Ueno zoo, but their twins, born in June 2021, will remain.

While sad to see the panda couple go, retiree Harumi Iteguchi took some comfort.

"Knowing that Ri Ri and Shin Shin will return together as a couple to their home country cheered me up a bit."