JAKARTA (AFP) - An impoverished sprinter who could not afford to buy his own running shoes has won the hearts of fellow Indonesians after his surprise victory in the 100-metre sprint at the world junior championships.

Lalu Muhammad Zohri, 18, on Wednesday (July 11) landed the first medal for an Indonesian athlete at the International Association of Athletics Federations (IAAF) World Under-20 Championships in Finland.

Social media lit up with messages of support from politicians, celebrities and other athletes in a nation rarely associated with track-and-field glory.

But it was Zohri's humble beginnings that drew the most attention.

The sprinter is from a village on the island of Lombok, next to Bali, where his family lives in a simple bamboo and wood home.

Zohri, whose parents are dead, had to ask his sister for 400,000 rupiah (S$38) to buy new trainers before the IAAF competition.

"I could only give him all the money I had. I am very proud of him," sister Baiq Fazilla tearfully told local media.

CNN Indonesia broadcast footage of Zohri's relatives bursting into tears when he crossed the finish line in 10.18 seconds - ahead of an American duo - as they watched the competition on a smartphone.

"He always used to like running around our village barefoot," his sister said.

"He never wore shoes because he didn't have any," she added.

Indonesian president Joko Widodo on Friday (July 13) called for local officials to renovate Zohri's humble home as he invited the new star to the presidential palace in Jakarta.

Zohri is set to compete next month at the Asian Games hosted by Indonesia.