"We received the video... and we are still busy investigating it," spokesman Prince Ndamase said.

Women and Men Against Child Abuse spokeswoman Vincentia Dlamini said she saw the video and referred it to Eyewitness News. It was then handed over to the FPB.

"The boy in the video is around three or four years old, while the girl is between eight and ten," she said.

"The girl seems to be leading the whole thing, and the boy is complying. Both of them seem to know what's happening. They perform acts that children, especially not at their age, would know about."

She said it wasn't clear whether the video was filmed in South Africa, but it was apparent that both children were African.

"All we are hoping for now is [for] someone to come forward and identify the children."

Police spokesman Lt-Col Lungelo Dlamini said he was not aware of the video.