Russian S-300 air defence missiles 'arrive in Iran'
Russia is reported to have started delivering S-300 surface-to-air missiles to Iran, under a deal opposed by Israel, the US and Saudi Arabia.
Iran's foreign ministry spokesman Hossein Jaberi-Ansari said "the first stage of the contract has been implemented".
It is not yet clear how many missiles may have been delivered.
The controversial contract got the go-ahead after last year's deal to lift international sanctions on Iran.
The diplomatic breakthrough involved a deal over Iran's atomic programme, imposing new international safeguards aimed at preventing Iran from developing nuclear weapons.
Iran has insisted its nuclear programme is for purely peaceful purposes and denies seeking to build a nuclear bomb.
The $800m (£562m) contract, signed in 2007, was frozen by Russia in 2010 because of the international sanctions. President Vladimir Putin unfroze it a year ago.
Israel and the US fear the missiles could be used to protect Iranian nuclear sites from air strikes.
The S-300, made by Rostec, can be used against multiple targets including jets, or to shoot down other missiles.
The S-300V4 variant, delivered to the Russian armed forces in 2014, can shoot down any medium-range missile in the world today, flies at five times the speed of sound and has a range of 400km (249 miles), Russia's Tass news agency reports.
Rostec chief Sergei Chemezov had told the Wall Street Journal last month that delivery of the system to Iran was expected at the end of this year.