Carrefour SA (CRRFY) shares slumped to the bottom of European markets Thursday after the world's second-largest retailer issued a profit warning for the second half of the year.

Paris-based Carrefour posted weaker-than-expected first half earnings of €661 million late Wednesday, down 21.5% from the same period last year, and slashed its full-year sales growth target to between 2% and 4% from a previous guidance of 3% to 5%. Sales for the six months ending in June were tabbed at €43.05 billion, the company said, up 3.3% from last year on a constant currency basis.

Carrefour shares were marked 13% lower in the opening minutes of trading, the steepest single-day decline in five years, to change hands at €17.24 each, taking their year-to-date slide past 35%.

New CEO Alexandre Bompard, who was named head of the group only last month, said he faces and "extraordinarily difficult" task in righting the ship at Europe's most import retailer, and vowed to accelerate plans to grow Carrefour's online business and "breathe new life" into the company's domestic operations. 

Carrefour is the latest global food retailer to feel the effect of Amazon's game-changing $13.7 billion purchase of Whole Foods Markets in June and its moves to slash prices by as much as 43% around the United State earlier this week. 

Activist shareholders have also been targeting food production companies to improve margins and cuts costs in a low inflation environment that has become increasing difficult to pass on price increases to customers.

Nestle shares hit a record high of Sfr86 earlier in July after activist investor Third Point LLC revealed it had built a 1% stake, worth around $3.5 billion, which would put the group among the ten largest shareholders of the Vevy, Switzerland-based group and said it wants management to pursue a series of options it argues would unlock shareholder value, including the sale of its 23% stake in luxury goods maker L'Oreal SA (LRLCY)

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