The arms trade adviser to President Vladimir Putin said Russia has begun delivering S-300 air defence missile systems to Iran, according to reports.
The S-300 deal has long worried Israel and other countries in the region, as well as the US, which see it as destabilising.
Russian state news agency Tass quoted Vladimir Kozhin as saying that the implementation of the contract for the delivery of the S-300s has begun and the deliveries have started. He did not provide any specifics.
In 2010, Russia froze a deal to supply advanced long-range S-300 missile systems to Iran, linking the decision to UN sanctions.
President Vladimir Putin lifted the suspension earlier this year following Iran’s deal with six world powers that curbed its nuclear programme in exchange for relief from international sanctions.
Officials said last month that Russia and Iran finalised the contract for their delivery.