An ICA employee in Stockholm cleans out a fridge after supermarket cooling systems across Europe were hit by temperature problems overnight.Photograph: Fredrik Sandberg/TT News Agency/AFP/Getty Images

Supermarket chains in Sweden, Belgium and Luxembourg have said the temperatures of their refrigerators and freezers in dozens of stores rose overnight, prompting fears of a cyber-attack similar to one that caused millions of euros of food losses in France.

Sweden's Coop chain told the daily Aftonbladet on Monday that six of ​its stores ‌had been ​affected, while ICA said it was "aware that a limited ​number of stores were affected by an incident overnight which impacted their refrigeration and freezer systems".