Autorita Garante della Concorrenza e del Mercato, Italy's antitrust body, said on Thursday it had opened a probe into allegations that Apple and Samsung Electronics used software updates to slow their mobile phones and push clients into buying new handsets.
The watchdog said that the two companies had not told clients that the updates might have a negative impact on the performance of their phones.
If found guilty, the two companies risk multi-million euro fines.
Apple acknowledged last month that iPhone software had the effect of slowing down some phones with battery problems, but denied that it had ever done anything to intentionally shorten the life of a product.
The company apologized for its actions and cut battery replacement costs. It has also said it would change its software to show users whether their phone batteries were working well.