STOCKHOLM/BRUSSELS/LONDON: A cyberattack targeting refrigeration systems at supermarkets spread across Europe on November 2, raising temperatures in fridges and freezers and forcing stores in several countries to throw away food.

The attack affected supermarket groups Ahold Delhaize and Colruyt in Belgium and Luxembourg, as well as Swedish grocers ICA and Coop. At least one IKEA store was also affected.

"Everything is destroyed," Engla Ingwall, sales manager at an ICA franchise store in Stockholm, told Reuters, adding that the attack occurred at 2 a.m. but was only discovered hours later.

"There has been a cyberattack and all our freezers reached 50 degrees (Celsius)."

ICA said a "limited number of stores were affected by an incident overnight, which impacted their refrigeration and freezer systems".

The incidents follow hackers seizing control of cooling units at hundreds of supermarkets in France last month, causing fires and food losses. Ahold also reported a cybersecurity incident to police last month.

No one has claimed responsibility for either attack, and it could not be established who was behind the incidents on November 2, or whether they were connected to those in France.

"It is not known who is behind this attack, and it may never be determined," said Katrien Eggers, spokesperson for Belgium's Center for Cybersecurity.

"All IT systems are potentially vulnerable, and AI can now be used to successfully exploit these weaknesses — especially by sophisticated actors," she said.

At least some of the refrigeration units affected on November 2 used temperature-control technology from Danish company Danfoss that was also targeted in the French attack. Danfoss said it had been working with customers to implement fixes.

The European Commission said the incidents demonstrated how disruptive digital threats were becoming.

"They are a deliberate attempt to disrupt our food supply chain and undermine consumers' confidence in it – a warning that we must take seriously," EU commissioner for agriculture Christophe Hansen said. "The repeated occurrence of these cyberattacks is deeply concerning."

Colruyt Group said five of its SPAR stores in Belgium had their refrigeration systems attacked.

In Ireland, wholesaler Musgrave said systems at 13 SuperValu stores were affected, forcing some chilled and frozen products to be removed from sale.

Carrefour said 15 of its 700 Belgian stores were affected, while IKEA said one store in Belgium had been hit and it could not rule out disruptions elsewhere.

Swedish grocery chain Coop said seven of its 800 stores were affected by unauthorized tampering with refrigeration systems.

Tom Hegel, a researcher at cybersecurity firm SentinelOne, said such attacks were typically associated with extortion, political motives or nation-state operations, while the lack of financial demands in recent cases pointed instead to sabotage.

"Retail is an easy target because retail chains run enormous estates of refrigeration controllers, building management systems, door access panels and point-of-sale gear," he said.

Belgian butchery chain De Laet & Van Haver was also affected. Founder Luc De Laet said refrigerators at one store had been turned up to as high as 18 C, ruining an estimated 15,000 euros (US$16,800) worth of meat.

"It's very scary. They are hacking the system that is doing the registration of the temperature, and they can program it at a distance," he said.