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Did Brandy play to a stadium of 89,960 empty seats on Saturday? The singer reportedly performed for a crowd of no more than 40 people at the end of a day-long arts and sports event in Johannesburg, South Africa, eventually walking off in embarrassment.

"Brandy [just] performed to an empty stadium. With the stadium lights on," tweeted an aghast South African musician, Kabomo. "People didn't know there was a concert after the games. No one knew Brandy was around. Maybe a 40 people audience ... She sulked after two songs and walked off."

The American R&B star was a surprise guest at the Nelson Mandela Sport and Culture Day, held at the 90,000-capacity FNB stadium in Soweto. Although tens of thousands of people filled the arena for football and rugby matches, including a game pitting South African football legends against Italian masters such as Emiliano Salvetti and Marco Ballota, the audience trickled out during the music segment. After performances by David Jenkins, Elvis Blue, Salif Keita and D'Banj, there was almost no one left for Brandy.

"Brandy performing for the chairs!" wrote one concertgoer. "Brandy is going to perform for herself and Mbaks only," marvelled another, referring to South Africa's minister of sport, Fikile Mbalula. She was even abandoned on television: SABC, the country's national TV channel, ended their broadcast of the concert before the singer came on stage.

Neither Brandy nor the concert promoters have commented on the gig. By most accounts, it wasn't Brandy's fault – her fans simply didn't know she was playing. Brandy is popular in Africa and has performed there before, much like in the UK, where she is due to return on 24 September. Although the singer's newest record, Two Eleven, reached only No 87 on the UK album charts, 1998's Never Say Never remains an R&B classic: it has sold more than 16m copies worldwide.