Nanjing, in east China's Jiangsu Province, used a centuries-old roof tile to kick off an online event to pass smiles around the world on Thursday, which was International Friendship Day.

With the hashtag "unlocksmilereunion," the event involved using social media to share images of smile-themed objects, such as cultural relics, paintings, sculptures and photography, among others, said Nanjing Week, the organizer of the event.

According to the organizer, over 40 cultural institutions worldwide, including Australia's National Gallery of Victoria and England's Manchester Museum, are involved in the smile relay, which has no particular end date.

Nanjing started the relay with an ancient roof tile that featured a smiley face, expressing hopes that people would draw courage from humanity's cultural relics to overcome difficulties.

The Manchester Museum, meanwhile, chose a smiling Buddha figurine. The museum's Twitter account said it "aims to create better understanding between different cultures" and smiling is a good way to achieve this.

Bryan Sitch, Deputy Head of Collections at the Manchester Museum, said that despite the COVID-19's impact on museums and galleries, they remained positive. "We look forward to the time when the threat of COVID-19 has been overcome and we can meet our friends in China again," Sitch said.