Hackers remotely raised temperatures in connected refrigerators and freezers at hundreds of supermarkets across France to as high as 50 degrees Celsius overnight, causing food losses and fires, according to the Paris prosecutor's office.

Intermarche owner Les Mousquetaires said around 150 of the company's stores were affected for six hours and all affected food was discarded to avoid health risks.

France's National Cybersecurity Agency is investigating the attack.