Russia's state arms exporter has described US sanctions against it as an "unfriendly act" aimed at undermining the Russian defence industry.
Russian jet-maker Sukhoi is one of the companies named
Rosoboronexport also denied that its dealings with Iran breached any international agreements.
The US last week imposed sanctions on two Russian firms for allegedly passing on equipment to Iran that could be used to develop weapons of mass destruction.
Five other firms in North Korea, India and Cuba were also penalised.
"The sanctions should be seen as nothing other than an unfriendly act against the Russian state and an attempt to destabilise its defence co-operation with foreign countries," a statement by Rosoboronexport said.
It said the company's co-operation with Tehran was "carried out strictly in accordance with international agreements and is limited exclusively to supplies of defensive armaments".
The other affected Russian company - aircraft manufacturer Sukhoi - earlier also denied the claims.
Last week, Sukhoi's chairman Alexander Klementiev told the Russian radio station Moscow Echo that it had delivered nothing to Iran for at least six years.
The Russian foreign ministry condemned the sanctions as a "clearly illegitimate" move.
The US State Department announced the sanctions on Friday.
It said the seven companies had broken US laws banning the sale to Tehran of equipment capable of helping the development of weapons of mass destruction.
The US sanctions were ordered under the 2000 Iran Non-proliferation Act.
They stop US firms working with affected companies.
A state department official, speaking on condition of anonymity, said the sanctions were imposed after the US obtained "credible information" that the companies had transferred equipment or materials to Iran since 1 January 1999.
"The sanctions apply to the specific entities and their successors, sub-units or subsidiaries and not to their respective countries or governments," the official told Reuters news agency.
Moscow last year signed a deal worth $700m (£380m) to supply up to 30 surface-to-air missiles to Iran.
The two Indian companies are Balaji Amines Ltd and Prachi Poly Products Ltd, both chemical manufacturers.
The North Korean companies are Korean Mining and Industrial Development Corporation and Korea Pugang Trading Corporation, and the Cuban company is the Centre for Genetic Engineering and Biotechnology.