The watchdog accused the companies of a "commercial policy aimed at exploiting the shortcomings of some (tech) components to reduce the performance of their products over time and persuade consumers to purchase new versions".
It said it was also looking into complaints the pair failed to provide information on what consequences software updates pushed by the companies would have on products.
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The Italian probe follows an investigation launched this month into Apple in France over suspected "planned obsolescence" in some of its iPhone models. The US company was forced to admit in December that it intentionally slowed down older models of its iPhones over time, sparking concerns it was unfairly nudging consumers to upgrade.
At the time, Apple denied it intentionally shortened the life on any of its products. It said it slowed models to extend the performance of the phone, which uses less power when running at slower speeds, and prevent unexpected shutdowns.
The California-based group also faces a class-action suit in the United States.
It has been a bad start to the year for Samsung too: the electronics giant faces a legal case in France over the alleged use of child labour and other abuses in Chinese manufacturing plants producing its products.