France has strict rules about the size of discounts that retailers can put on products outside of official sales periods.
Last week, shoppers at Intermarché shops jostled to buy heavily discounted chocolate and hazelnut spread.
It had been discounted by 70% - from €4.50 (£3.90) to €1.40.
Police were called when people began fighting and pushing one another.
"They are like animals. A woman had her hair pulled, an elderly lady took a box on her head, another had a bloody hand," one customer told French media.