An Australian mother was aghast as she saw her four-year-old child almost got kidnapped right before her very eyes.

The unidentified 25-year-old mother went shopping on Wednesday at about 5pm at the Safeway supermarket on Thompsons Rd, Cranbourne. Along with her were her three children, the youngest of which was the four-year-old child.

While checking out the wares in a grocery aisle, she saw a woman approach her children who were huddled together around the shopping cart.

The woman, who was described to have dark hair and about 170 centimetres tall with a thin build, apparently argued with the eldest of the children that the youngest child was hers.

A short time later, when the youngest child started to roam in the toy aisle, the woman picked the child up, right before the young mother's very eyes.

Immediately, the young mother accosted the woman, who in turn immediately brought the child down and then fled the supermarket premises.

The young mother was shaking nevertheless.

"This type of thing seldom happens but when it does it's probably one of the most confronting and scary things that a parent can ever face," Detective Leading Senior Constable Chris Russo was quoted by the Daily Telegraph.

"The children are obviously upset but particularly the mother is also quite upset,"

Unfortunately, the incident was not captured on CCTV, the police said.