U.S. officials confirmed on Tuesday that an American MQ-9 Reaper drone destroyed a Russian-made T-72 battle tank in Syria on Sunday, after U.S. special operations troops and their Syrian allies came under attack by forces supporting dictator Bashar Assad.

“The tank had been maneuvering with coordinated indirect fire on a defensive position occupied by Syrian Democratic Forces and Coalition advisers. The defensive position was within effective range of the tank’s weapon system,” said a statement from the U.S. Central Command quoted by Fox News.

“Coalition officials maintained regular contact with Russian counterparts via established de-confliction lines to avoid misperceptions and miscalculations that could endanger each other’s forces,” the statement added. The three-man crew was reportedly killed in the drone strike, while the U.S. coalition suffered no casualties.

NBC News quotes coalition spokesman Col. Ryan Dillon explaining that the tank itself was not firing on U.S. and SDF forces, but was part of a formation in which “other elements” were firing. The attackers were reportedly using mortars and small arms in an effort to push the Syrian Democratic Forces back from a position near al-Tabiyeh in eastern Syria. Their strategic objective may have been securing a nearby oil field.

According to Central Command, the pro-regime forces involved in Sunday’s incident were from the same group that attacked U.S. special operators and Syrian fighters on February 7 and 8.

It was eventually revealed that Russian military contractors were mixed in with the Assad regime’s allies in that attack, and a number of them were killed.

The Russians claim a handful of Russian “paramilitary contractors” were killed in the battle, while the Syrian government says U.S. troops and their allies killed almost a hundred Russians. CNN identified several of the slain Russians on Tuesday; they were portrayed as a mixture of mercenaries and “ultranationalists.”

CBS News notes that whatever their motivations for fighting in Syria, the casualties from last week’s battle constitute the first Russians killed by U.S. airstrikes in Syria. CBS also notes the interesting fact that some Turkish forces were present at the SDF headquarters alongside the Americans, even as tensions between the U.S. and Turkey are mounting near the Turkish border.

“The Kremlin – seeking to play down its involvement in the fighting in Syria and seemingly hoping to avoid escalating tensions with the United States – has sidestepped questions about the episode,” the New York Times wrote of Sunday’s drone strike on a Russian-made tank.

“It was self-defense. Obviously, we are not getting engaged in the Syrian civil war,” Secretary of Defense James Mattis said of the U.S. strikes over the weekend.

Mattis said the Russians told American officials there were no Russian forces involved in the attack, even though Russians have now been discovered among the dead. He described the entire situation around al-Tabiyeh “perplexing” and said he could see no reason for the Assad regime’s attack on the SDF headquarters.