A top Iranian lawmaker confirmed Wednesday that Russian warplanes are using an airbase on its territory, as Moscow announced it conducted another airstrike in Syria with jets that took off from Iran.
The operations have been authorized by Iran's Supreme National Security Council and are based on a deal between Iran, Russia, Syria and Iraq, the head of parliament's national security committee, Alaeddin Boroujerdi, said in comments carried by Iranian state news agency IRNA.
He specified that the jets were using the Nojeh airbase in Iran's western Hamadan province to refuel. Hamadan is much closer to positions of the Islamic State extremist group than the base Russia had previously been using, Khmeimim, in coastal northern Syria.
"The matter should be considered a strategic and necessary cooperation in the fight against terrorism," said former Iranian foreign minister Ali Akbar Velayati, who is currently a foreign policy adviser to Iran's supreme leader.
The cooperation does not violate UN resolutions and has been approved by Syria, he said.
Earlier, the speaker of Iran's parliament, Ali Larijani, denied that Russian warplanes were using Iranian territory.
Russia attested Wednesday that its use of the Iranian airbase does not violate UN Security Council Resolution 2231, which forbids the supply, sale or transfer of combat aircraft to Iran without prior approval.
US State Department spokesman Mark Toner told reporters Wednesday that State Department lawyers were in the process of assessing the legality of the flights. Russia would have an opportunity to make its case to the Security Council if the US did raise questions, he said.
US Air Force Secretary Deborah Lee James told reporters in New York that Russia's move to launch attacks from an Iranian airbase was "yet again another complication in an already very complex environment."
She said Russia had notified the US that its jets would take off from Iran in what she called "a little bit of an advance warning" to avoid accidents or the Russian planes being shot down by mistake.
"There is no broader coordination. There is nothing beyond safety of flights," James said.
It is unclear how long Russia intends to use the Iranian airbase.
"Whether it's a permanent thing, whether it's a temporary thing - I have no idea," James said.
Russia and Iran are longtime allies of Syrian President Bashar al-Assad. Russia and the US support opposing sides in Syria but agree on the need to eliminate UN-designated terrorist groups, such as the Islamic State movement.
The Russia Defence Ministry said Wednesday that Su-34 warplanes took off from the Iranian airbase and conducted an airstrike against Islamic State targets in the Syrian province of Deir al-Zour.
The attack hit two Islamic State command points and large training camps, "eliminating more than 150 militants," the ministry said in comments carried by TASS.
On Tuesday, Russian warplanes used an Iranian airbase for the first time for military actions in Syria.