A Cape Town school is investigating allegations of racist bullying after a video emerged that appears to show pupils pretending to auction off their black classmates, the provincial education department said Friday.

The video shared on WhatsApp and leaked to the media shows at least two male black pupils behind a gate in a fenced-off area as several mixed-race "coloured" students appear to be shouting bids for them.

The video, entitled "Slavery at school is crazy", was "deeply disturbing and hurtful", Western Cape Education Department spokesperson Bronagh Hammond said.

The school has opened a disciplinary investigation into allegations of racist bullying, she said.

News24 cited a parent as saying that a group of boys had tried to force her son into a cage but he escaped.

"They were picking up black boys and putting them in the cage," the unidentified woman was quoted as saying.

Although a minority nationally, mixed-race South Africans who identify themselves as "colored" mostly live in the Western Cape province, of which Cape Town is the capital.

Allegations of racism at South Africa schools persist 30 years after the first all-race election in 1994 put an end to white minority rule under the apartheid system.

Twelve white pupils from the Pretoria Girls High School were suspended this week for allegedly making racist comments against their black classmates in a WhatsApp group.