Iran's military muscle worries the US and Israel

Russian Defence Minister Sergei Ivanov said a contract to deliver TOR-M1 missiles to Iran had been signed.

He said the deal "in no way upsets the balance of forces in the region," Russian news agencies reported.

Iran has reportedly agreed to buy 29 of the mobile air defence systems in a contract worth more than $700m (£400m; 600m euros).

The BBC's Steve Rosenberg in Moscow says the sale is not banned under any treaty, but it has already been criticised by the United States and Israel.

Earlier, Iran announced that it was planning to build a second nuclear power plant in the south of the country, despite coming under pressure from the international community over its nuclear ambitions.

Iran has previously said it wants to build 20 nuclear power stations in as many years.

Earlier this year the Russian government faced criticism from the West when Moscow agreed to sell missile systems to Syria.