Russia has reportedly picked up its first batch of Iranian-made combat drones that it intends to use on the battlefield during its ongoing invasion of Ukraine.

U.S. officials say that Russian cargo planes departed Iran on Aug. 19 carrying at least two types of combat capable drones, the Washington Post reported Monday.

The Mohajer-6 and Shahed-series drones are believed to be the first of many shipments from Iran to Russia as part of the Kremlin’s plan to increase its attack drone capability in the war with Ukraine.

The deal between the two nations was reportedly negotiated over several months and included Iranian technical experts traveling to Russia to help set up systems as well as Russian military operatives traveling to Iran for training. 

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Valdimir Putin stands next to Russian military officer at military forum

Russian President Vladimir Putin (left) vows to strengthen Russia's military cooperation with its allies at the Army 2022 International Military and Technical Forum in the Patriot Park outside Moscow, Russia, on Aug. 15, 2022. (Sputnik, Kremlin Pool Photo via AP)

While the drones could provide Russia with a boost on the battlefield, U.S. officials reportedly said that Iranian drones have been the source of headaches and technical issues for the Russians.

"There are a few bugs in the system," an unnamed official told the Washington Post.  "The Russians are not satisfied."

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The Washington Post reported that Russia has 1,500 to 2,000 military surveillance drones as part of its Ukraine campaign but does not possess many combat capable drones. On the other side, Ukraine has been deploying Turkish-made combat drones that have been effective against Russian targets.

Putin and officials in sharp suits arrive at airport in Tehran, Iran

Russian President Vladimir Putin, center, upon his arrival at an International Airport outside Tehran, Iran, Tuesday, July 19, 2022.  (Konstantin Zavragin, Sputnik, Kremlin Pool Photo via AP)

On Tuesday, Russian Presidential Spokesman Dmitry Peskov dismissed the Washington Post report as "fake."

Rebekah Koffler, a former U.S. DIA intelligence officer focused on Russia and the author of "Putin's Playbook: Russia's Secret Plan to Defeat America," told Fox News Digital that it is not clear why the Kremlin is denying the report, but what is clear is that Peskov "cannot be trusted."

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"It is possible that Putin’s control of what Peskov says in terms of denying drone deliveries from Iran to Russia is to confuse Ukrainian and Western intelligence in order to achieve some operational secrecy and tactical surprise for the Russian forces," Koffler said. "Ukraine will likely be targeting these drones for destruction, which raises the threat concerns for the Russians, especially in light of recent mysterious attacks on ammunition depots and other targets in Crimea."