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”.

The Dutch retailer Ahold Delhaize, which last ​month ​reported a ​cybersecurity ‌incident ​to police in the Netherlands, said an “IT incident” ​had hit fridges and ⁠freezers in dozens of its ⁠supermarkets in ​Belgium ‌and ‌Luxembourg.

A company spokesperson, Sarah ‌De Meester, said the supermarket chain had established that temperatures in the cooling systems had increased, adding that the incident was being investigated.

Belgium’s Le Soir newspaper reported that dozens of stores and supermarkets were affected, including five Spar outlets, multiple Shop & Go convenience stores attached to Q8 service stations, and a number of smaller Proxy Delhaize minimarkets.

“We started mobilising technicians at 1am,” Stephan Moelans, the chief executive of Sabcobel, which specialises in refrigeration system installations, told the paper. “We spent all night and morning disconnecting the affected installations from the grid.”

French ⁠police said in October that hackers had seized control of cooling units at ⁠up to 700 supermarkets in a large-scale attack that led to heavy losses of chilled and frozen foods and underlined the vulnerability of internet-connected systems.

Hackers had remotely overridden the settings on thousands of freezers, fridges and chiller cabinets, pushing them from as low as -27C to well over 50C. The Intermarché, Coopérative U, Carrefour, Leclerc and Monoprix chains were among those affected.

Stores had to discard vast quantities of fresh meat, dairy and frozen products, with many suffering losses ranging from tens of thousands of euros to more than €130,000 (£109,000). Two stores in Alsace reported a combined loss of €270,000.

Most supermarket cold aisles are connected to the internet to allow remote maintenance and alerts for system failures. In the French attack, the hackers pirated controllers mostly supplied by the Danish company Danfoss.

skip past newsletter promotion Free newsletter | Every day Sign up to Headlines Europe A digest of the morning's main headlines from the Europe edition emailed direct to you every week day Enter your email Sign up after newsletter promotion

They disabled alarm systems before adjusting the thermostats or extending the defrost programme by hours. Danfoss said it had identified security flaws last year and had “long recommended” customers install updates.

The Paris prosecutor’s office has opened a formal investigatiion into the French attack, saying damage included “food losses and fires”, and the prime minister, Sébastien Lecornu, instructed France’s national cybersecurity agency, ANSSI, to investigate.

ANSSI subsequently confirmed that supermarkets using controllers from two other companies were also targeted in the attack.