The news reports said Russian was selling Iran advanced missiles and other systems, but the Foreign Ministry spokesman, Mikhail Kamynin, did not comment on specifics, saying in a statement only that they were "exclusively defensive weapons."
Kamynin said the sales fully complied with nonproliferation commitments and Russian law.
The statement appeared timed to head off the heated reaction expected from the United States after Russian media reported Friday that officials had signed contracts in November that would send up to 30 Tor-M1 missile systems to Iran over the next two years.
The Interfax news agency said the Tor-M1 system could identify up to 48 targets and fire at two targets simultaneously at a height of up to 20,000 feet.
A high-ranking Iranian official downplayed the deal, telling the official Islamic Republic News Agency on Saturday that Iran buys arms from many countries and would not stop.
"Iran's and Russia's military cooperation is not a complicated issue," said Ali Larijani, secretary of Iran's Supreme National Security Council. "It existed before, and there was no ban on it."
On Friday, Israel carried out a successful test of its Arrow missile defense system, intercepting and destroying a missile similar to Iran's long-range Shahab-3.
Israel considers Iran its biggest threat, and does not believe the Muslim theocracy's claims that its nuclear program is peaceful. Israeli concerns were heightened recently after Iranian President Mahmoud Ahmadinejad urged that Israel be "wiped off the map."