A Chinese man needs two million yuan (US$285,000) to pay for his wife’s cancer treatment has been unexpectedly gifted 50 tonnes of sweet potatoes by a mystery donor.

He began selling the starchy root vegetables at a street stall and used the proceeds to pay his wife’s medical bills, moving countless people on mainland social media.

Recently, 35-year-old Jia Changlong was spotted selling the potatoes in Jinan, Shandong province in northern China.

Jia, from Dezhou, Shandong, and his wife, surnamed Li, a housewife, were secondary school classmates. The couple now live in Yantai, Shandong province, and has an eight-year-old son.

In July, Li was diagnosed with acute myeloid leukaemia. After undergoing initial treatment, she is now recovering at home.