A controversial painting showing South Africa's President Jacob Zuma with his genitals hanging out has been vandalised in an art gallery.
The BBC's Andrew Harding at the gallery in Johannesburg said two men covered the art work in black and red paint
It comes as the governing ANC was asking the High Court to force the Goodman Gallery to remove the painting.
The $14,000 (£9,000) 1.85m-high Soviet-style, red black and yellow acrylic painting had already been sold.
Called The Spear, the painting is by Brett Murray, who is known for his political and provocative work.
Footage shown on local television showed a man in a suit painting a red cross over the president's genital area and then his face, AP news agency reports.
Then another man, wearing a hooded top, rubbed black paint over the president's face and down the painting with his hands.
"The white middle-aged man was the one who started it off and a young black man finished it off," Lance Claasen, a Khaya FM radio reporter who witnessed the defacing, told the AFP news agency.
Our correspondent says he saw one man wielding the paint brush, who was then pounced on by security guards and head-butted at one point.
"I'm doing this because the painting is disrespectful to President Zuma," one of the men told the BBC.
The African National Congress has described the work as "rude, crude and disrespectful".
Earlier a crowd of ANC supporters had gathered near the court house in Johannesburg where the ruling party's challenge to get to the painting removed was being heard.
It was decided that a full bench of the High Court would hear the case on Thursday.
"This is a matter of great national importance," the South African Press Association quotes Judge Kathree Setiloane as saying.
The exhibition at the Goodman Gallery opened earlier this month and was scheduled to close on 16 June.
The ANC is also demanding that the City Press newspaper remove a photograph of the painting from its website.
In an affidavit served on the paper, Mr Zuma said he was shocked by the work saying: "The portrait depicts me in a manner that suggests I am a philanderer, a womaniser and one with no respect. It is an undignified depiction of my personality and seeks to create doubt about my personality in the eyes of fellow citizens, family and children."
"It is an undignified depiction of my personality and seeks to create doubt about my personality in the eyes of fellow citizens, family and children," South Africa's Sunday Independent quotes his statement as saying.
President Zuma, who has four wives, has sued local media companies 11 times for defamation - some of which has been settled, others dropped, but most are outstanding.
The best-known case is a 2008 suit against one of the country's most high-profile artists, Zapiro, after he depicted Mr Zuma about to rape a female figure representing justice - this is due to be heard in October.
Mr Zuma was cleared of raping a family friend in 2006.
Two years ago, the ANC condemned a painting on show at a Johannesburg shopping centre that depicted the body of Nelson Mandela undergoing an autopsy, saying it violated the anti-apartheid icon's dignity.