Russia starts using an Iranian airbase to launch attacks into Syria. [Photo: Xinhua]

Russian authorities are rebuffing US claims that Russia is violating UN sanctions on Iran.

This follows a move this week by Russia to start using an Iranian airbase to launch attacks into Syria.

Russian Foreign Minister Sergei Lavrov says the allegations being made by the US State Department are completely untrue.

"There is no reason whatsoever to suspect Russia's violation of Resolution 2231 because there has been no supply, sale or transfer of military aircraft to Iran from Russia."

Under that UN resolution, any sale of military equipment to Iran has to get Security Council approval.

Lavrov says the Russian air strikes being launched from Iran have been approved by Iran and are being carried out at the request of the Syrian government to help in fighting against terrorist groups.

Lavrov also says the Russian and US sides have been meeting to implement a cooperation agreement on Syria reached between the two countries last month.

That deal would see the two sides coordinate their campaigns.

To this point, Russian and US forces have been acting separately in Syria, though they have a mechanism in-place to ensure their forces don't accidentally open fire on one-another.