Two men were taken into police custody accused of vandalising a portrait of South African President Jacob Zuma with his genitals exposed.
Zuma's African National Congress (ANC) party had already launched a legal bid to try to force the Goodman Gallery to remove the controversial picture, which it described as crude and racist.
Earlier ANC Secretary General Gwede Mantashe said: "Genitals hanging there is not a debate, it's an insult, that's my starting point and that's where I stop."
The scandal of the portrait, the president, his privacy and his genitalia has captivated South Africa.
South Africa's president Jacob Zuma has gone to court in a bid to remove a painting of him with his genitals exposed removed from a gallery.