Police are investigating a case of common robbery after a woman was targeted outside her child's school in the Johannesburg suburb of Greenside. 

According to police, the victim was on her way to fetch her child from school on Wednesday, along Barry Hertzog Avenue, when she was approached by the assailant.

Captain Tintswalo Sibeko, from the Parkview police, said a man had jumped out of a vehicle and grabbed the woman's cellphone, but had failed to get hold of her car keys.

In a video posted online, the woman can be seen in a brief tussle with the alleged robber on CCTV.

He then throws her to the ground, before jumping into a vehicle parked on the side of the road.

"He was trying to get my keys," a woman, presumed to be the victim, can be heard saying in the video.

"He swung me quite hard to the floor. I didn't realise in the moment," she adds.