Russia has accused American technology giant Apple Inc. of allegedly fixing retail prices of its iPhones in the country.

Russia's Federal Anti-monopoly Service (FAS) said Monday an investigation found that retailers "set identical prices" for iPhone 6s, iPhone 6s Plus and other iPhone models and kept the prices at that level for a certain period of time.

Targets of the investigation are Apple's Russian operation, known as Apple Rus, Apple Inc., three other Apple business entities and 16 of the company's primary resellers in Russia.

MTS, one of the resellers targeted by FAS, declined a request for comment. Another firm, Euroset, denied allegations of price fixing.

Apple, which was not immediately available for comment, has previously been the target of a Russian price-fixing investigation. As a result of the probe, two Russian mobile businesses were fined for fixing prices for iPhone 4.

FAS said it launched the investigation in response to a complaint from a consumer who noticed the prices remain unchanged since the 2015 introduction of the two new models in Russia.