Thousands of people are expected to march Tuesday in South Africa to protest a portrait of President Jacob Zuma that shows his genitals.

Zuma's supporters in the ruling African National Congress say the portrait is insulting and call it an attack on both the president and his party.

About 15,000 people are expected to participate in the march to Johannesburg's Goodman Gallery, where the work was on display, according to the South African Broadcasting Corporation.

The painting by artist Brett Murray, called "The Spear," is reminiscent of Soviet-era propaganda posters. Red on one half and black on the other, the painting shows Zuma in a proud stance with his genitals prominently exposed.