Washington CNN  — 

The United States has “abundant evidence” that Russia is using Iranian drones to strike Ukraine, State Department spokesperson Ned Price said Wednesday.

“The United States began warning in July that Iran was planning to transfer UAVs to Russia for use in Russia’s brutal war against Ukraine, and we now have abundant evidence that these UAVs are being used to strike Ukrainian civilians and critical civilian infrastructure,” Price said in a statement.

The United Nations Security Council received expert briefings on Iran’s transfer of such drones to Russia, Price said, and the issue was collectively raised by the US, United Kingdom and France at a closed-door UNSC meeting Wednesday.

Drones have played a significant role in the conflict since Russia launched its full-scale invasion of Ukraine in late February, but their use has increased since the summer, when the United States and Kyiv say Moscow acquired the drones from Iran. Iran has denied supplying weapons to Russia despite evidence to the contrary.

CNN reported Tuesday that Iran has sent military personnel to Russian-occupied territory inside Crimea to train and advise the Russian military on the use of their drones, according to two sources familiar with US intelligence.

A spokesman for the Iranian mission at the United Nations said, “Iran does not confirm this claim and rejects it.”

Iran’s UN Ambassador Amir Saeid Iravani denied his country supplied Russia with drones for use in Ukraine and told reporters the West was running a disinformation campaign against Iran.

“Iran categorically rejected unfounded and unsubstantiated claims that Iran has transferred UAVs for the use (in) the conflict in Ukraine,” Iravani said during a news conference from New York.

Russian Foreign Ministry spokesperson Maria Zakharova said on Thursday that reports Russia is using Iranian UAVs are “unsubstantiated inferences” and “far-fetched assumptions,” despite ample evidence of their use in Ukraine.

Still, the US has said there will be consequences for these Iranian drone transfers to Russia, and Price dangled the possibility of sanctions being rolled out. “We will not hesitate to use our sanctions and other appropriate tools on all involved in these transfers,” he said.

Kamikaze drones, or suicide drones, are a type of aerial weapon system. They are known as a loitering munition because they are capable of waiting for some time in an area identified as a potential target and only strike once an enemy asset is identified.

They are small, portable and can be easily launched, but their main advantage is that they are hard to detect and can be fired from a distance.

CNN’s Niamh Kennedy, Negar Mahmoodi, Ivana Kottasová and Andrew Raine contributed to this report.