Seven weapons experts flew from Moscow to Tehran on April 24 and September 17 last year, according to the report.
Their trips occurred amid heightened tensions between Iran and Israel, as both countries exchanged military strikes in the same months.
The report, citing a senior Iranian defense ministry official, said Russian missile experts had visited multiple Iranian missile production facilities last year, including two underground sites. Some of these visits took place in September, the official said, without specifying locations.
A Western defense official cited by Reuters said that Russian missile specialists visited an Iranian missile base west of the port of Amirabad on Iran’s Caspian Sea coast in September.
According to Reuters, all seven Russian experts have military backgrounds.
The report said that a review of Russian databases showed that two hold the rank of colonel, two are lieutenant-colonel, and others specialize in air-defense missile systems, artillery, rocketry, advanced weapons development, and missile testing.