Britain’s cyber security chiefs have alerted retailers after hackers took control of supermarket fridges across Europe, with attacks affecting 70 stores on the Continent.

The shutdowns have raised concerns about food security. The incidents involve interference with refrigeration itself, putting an essential part of supermarket operations at the centre of the cyber security warning.

The alert brings the risk to British retailers’ attention, although the reported attacks concern stores in continental Europe. How long the fridges were shut down, whether food was lost and the extent of any disruption to shoppers remain unclear.