Joint Chiefs Chairman Gen. Joseph Dunford called his Russian counterpart, Gen. Valery Gerasimov, following a swarm drone attack on a Russian air base in Syria earlier this week, Pentagon officials said Thursday.

Marine Lt. Gen. Kenneth McKenzie, the Pentagon's Joint Staff director, said only that Dunford and Gerasimov, the chief of Russia's General Staff, had a "frank and cordial exchange of views," but the phone call came after the Russian Defense Ministry suggested the U.S. may have played a part in the drone attack.

While declining to characterize the phone call, McKenzie stressed that "the U.S. had nothing to do with the attacks on the Russian air base and that's a flat assertion, and I want to be very clear on that."

Russia's Ministry of Defense said Monday that its vast Khmeimim air base in Syria's northwestern Latakia province had been the target recently of a series of attacks by small unmanned aerial vehicles carrying miniature bombs, including at least one swarm attack.

The Russian naval base at Tartus was also the target of the drones, the ministry said.

The ministry said there were no casualties or damage from the attacks by "small-sized air targets of unknown identity."

Seven were shot down and three others exploded after crashing on the night of Jan. 5, the ministry said.

The drone attacks were the first time that "terrorists" had employed a "massed drone aircraft attack launched at a range of more than 50 [kilometers] using a modern GPS guidance system," the ministry said.

The attacks came about a week after two Russian troops were killed in a mortar attack on Khmeimim.

On Wednesday, the ministry said the launch site for the drones was in the southwestern region of Idlib province, to the north of Khmeimim, where several rebel groups operate in the ongoing war against the regime of Syrian President Bashar al-Assad.

While not directly accusing the U.S., the ministry charged that a U.S. Navy P-8 Poseidon surveillance aircraft flew over the general area at the time of the drone attacks, calling it a "strange coincidence."

The ministry also said that those behind the attacks would have needed help from "countries with high technological capabilities."

However, it noted that Turkish forces also operate in the general area from which the drone attacks allegedly were launched.

The ministry said letters had gone out to the Turkish forces stressing "the need for Ankara to fulfill its obligations to ensure compliance with the [Syrian] regime for the cessation of hostilities."

At the Pentagon, McKenzie said Dunford's phone call to Gerasimov was one of numerous channels that the U.S. uses to "deconflict" American forces operating in Syria in partnership with the anti-ISIS Syrian Democratic forces from the Russian air and ground forces backing the Assad regime.

"We maintain communications with the Russians on what goes on in Syria at a variety of levels," he said.

"We believe that deconfliction is an effective technique to allow us to pursue our goal of destroying" the Islamic State of Iraq and Syria, whose remnants have been reduced to holding isolated areas of Syria's middle Euphrates River Valley, McKenzie said.

-- Richard Sisk can be reached at Richard.Sisk@Military.com.