The authority said it suspected that the retail giant had been giving preferential exposure to third-party vendors on its platform only if they subscribed to Amazon's logistics service.
“These practices would have allowed Amazon to profit unfairly from its dominant position” in online commerce platforms “in order to significantly curtail competition” on storage and dispatch markets, said the Italian competition authority, Antitrust. These practices would have in the end harmed consumers, it added.
The investigation is likely to last a year, said Antitrust. The authority's agents inspected various Amazon sites on Tuesday, accompanied by members of the financial crime unit.
The Italian case follows probes by authorities in Japan, France, Austria and the EU Commission into practices by Amazon and other tech giants like Google, Apple and Facebook.
In June 2017, the EU Commission hit Google with a fine of €2.42 billion for abuse of its dominant market position, the first such sanction for the company in Europe.