Shares in Carrefour have fallen 6% after Europe's biggest retailer issued a warning that profits in its core French market were set to fall.
Carrefour, which issued two profit warnings last year, is facing fierce competition from rivals in France.
The company said late on Thursday that first-half results would be below expectations.
Analysts had feared a warning since May, when the head of operations in France unexpectedly left the company.
Carrefour, the world's second largest retailer behind Wal-Mart, has been under pressure from rivals E Leclerc and Auchan.
Carrefour shares have now fallen 14% since the start of the year.
Chief executive Lars Olofsson had taken personal control of the French business, while at the same time delivering a global turnaround strategy.
But on Thursday Carrefour announced that it had named company veteran Noel Prioux to take charge of its French operations.
France accounts for 40% of Carrefour's sales and is under pressure as rivals keep prices low to gain market share.