Members of the Islamic Revolutionary Guard Corps (IRGC) may have traveled to Russian-held territories in Ukraine in order to help train Russian troops. The IRGC is designated by the U.S. as a Foreign Terrorist Organization (FTO.)

A report by the Institute for the Study of War (IFSW), published last week, said that Russian forces "may have" brought IRGC-affiliated personnel to train the troops in the use of the Shahed-136 drones – another example of the warming relationship between Moscow and Tehran. 

The IFSW draws on a report by the Ukrainian Resistance Center posted Oct. 12 in which it claims an "unspecificed" number of instructors from Iran arrived in Dzankoi in Crimea, Zalizniy Port and Hladivtsi in Kherson Oblast. 

British outlet The Daily Mirror said the number could be "up to 50" IRGC specialists, but the IFSW told Fox News Digital that it did not have a specific number. 

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The Pentagon told Fox News Digital it had "nothing to add at this time" in response to the reports. 

The Resistance Center also claimed that the Iranian instructors directly control the launch of drones on civilian targets, including in the Mykolaiv and Odesa oblasts.

Iranian Revolutionary Guard Corps

Iranian Revolutionary Guard members arrive for a ceremony celebrating the 40th anniversary of the Islamic Revolution in Tehran, Iran, on Monday. The co-conspirators named in the indictment are accused by the Justice Department of working on behalf of the military unit. (AP)

While the Resistance Center only specified that the instructors are Iranian, the IFSW noted that the IRGC is the primary operator of Iran’s drone inventory, making it "likely" the instructors are either IRGC members or at least affiliated with the group. 

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Russia has intensified its bombing attacks in the wake of the Crimea bridge blast, firing 80 cruise missiles into Ukraine as "retaliation" for the "attack" on the Kerch Bridge. 

Iran drone

This undated photograph released by the Ukrainian military's Strategic Communications Directorate shows the wreckage of what Kyiv has described as an Iranian Shahed drone downed near Kupiansk, Ukraine. Ukraine's military claimed Tuesday, Sept. 13, 2022, for the first time that it encountered an Iranian-supplied suicide drone used by Russia on the battlefield, showing the deepening ties between Moscow and Tehran as the Islamic Republic's tattered nuclear deal with world powers hangs in the balance. (Ukrainian military's Strategic Communications Directorate via AP) (Ukrainian military's Strategic Communications Directorate via AP)

The explosion of a fuel tank damaged part of the bridge, which connects Russia with the Crimean Peninsula, causing part of the structure to fall into the water, Russian officials said. Three people died in the explosion – presumably passengers in a car next to the truck that exploded. 

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Tehran has repeatedly claimed that it is not involved in Russian President Vladimir Putin’s war in Ukraine, but critics questioned that position as Shahed-136 drones, also known as "kamikaze drones," started to appear on the front lines. 

Buildings destroyed in Ukraine

A local resident walks next to an apartment building destroyed in a Russian shelling in Kramatorsk, Ukraine. Two American were reportedly killed in the country.  (AP Photo/Andriy Andriyenko)

Moscow received the drones over the summer as officials turned to North Korea and Iran to help refres dwindling arms supplies, including artillery shells and rockets. Russian troops ran into technical problems trying to deploy the Shahed-136 drones, but they started to use the drones in mid-September, as Ukrainian troops claimed to have shot some of the drones down. 

"The loss of a Shahed-136 near the front lines suggests there is a realistic possibility that Russia is attempting to use the system to conduct tactical strikes rather than against more strategic targets further into Ukraine territory," a British defense ministry report stated.

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Kyiv residents last week awoke to air raid sirens as the drones struck somewhere along the perimeter of the capital city, with casualties remaining unknown. However, deputy head of the presidential office Kyrylo Tymoshenko said on Telegram that the attack impacted "critical infrastructure facilities" 

Fox News’ Lawrence Richard and Andrea Vacchiano contributed to this report.