Their deaths are not listed as casualties by the Russian government, meaning the true cost of Russia's intervention could be higher than the official count.
As to who they killed, U.S. officials are no more forthcoming than they ever are, with Lt. Gen. Harrigian saying the USA is "not going to speculate" on who they killed, and that they flat out don't know whose tank it was, or who was driving it.
The Russian Defense Ministry charged that the incident reflected a USA push to grab Syria's economic assets under the cover of fighting the Islamic State group.
On Wednesday, U.S. forces struck pro-Assad forces after they started what the U.S. military described as an "unprovoked" attack on the U.S. -backed Syrian Democratic Forces.
The strike was the second by the US against pro-Syrian regime forces last week, according to the USA military's Central Command.
USA defense secretary Jim Mattis on Tuesday said he is aware of claims that Russian fighters were among those killed by coalition strikes, but said that he could not confirm the reports, according to Reuters.
That could cause another potential global escalation of this seven-year-old fight, which began as a civil war between Assad and his domestic detractors.
The Kremlin on Tuesday said it had no information about the alleged killing of Russian mercenaries during last week's coalition airstrikes on pro-government forces in Deir Ezzor province, Reuters reported.
The air force general said the United States was in contact with Russian Federation before carrying out the defensive strike.
He said that talk of "separatist inclinations" by some sides are the results of the American actions as they have misled those sides into thinking will remain under the United States custody and protection no matter what they do, which also caused a reaction from Turkey.
The Russian Defence Ministry has insisted its troops were not involved in the incident. Like many contractors who have gone to Syria, he was a member of a Cossack group of ultranationalists who have also fought in eastern Ukraine.
It also noted pro-government forces that advanced toward the area under control of the US-supported forces had failed to coordinate their action with the Russian military in Syria. We can only operate data on the servicemen of Russian Armed Forces, who take part in the operation of the Russian Airspace forces supporting the Syrian Army.
"Those steps look increasingly as part of efforst to create a quasi-state on a large part of Syrian territory, from the eastern bank of the Euphrates River all the way to the border with Iraq", he went on. The U.S. military accepted the claim, while Defense Secretary Jim Mattis called the whole affair "perplexing".
Averin said he believed that casualties among the Russians present amounted to more than "the typical Wagner loss of just a couple of people". "I'm not willing to say that the Russians have lost influence or gained influence". "I can't give you anything on that".
The U.S.is in talks with Russian Federation now in search of an explanation for what happened, said two administration officials who asked not to be identified discussing private conversations. Mercenaries, who've been active in the conflicts in eastern Ukraine and Syria, allow Russian Federation to deny official involvement in operations when things go wrong.
This incident comes at an odd time for the two countries. Grigory Yavlinsky, a politician running for president in Russia, called on Putin to reveal exactly how many Russians were killed in Syria. He noted that the Russian military could have been unaware of the contractors' involvement in the attacking force because coordination between them has been very poor.
It is unclear who was paying the Russian mercenary group, with reports in Russia signaling that Wagner-the Russian equivalent to the US' Blackwater-was hired by Assad or his allies. Vladimir Putin is running for re-election on March 18.
Moscow's reticence on the matter underlines a key Kremlin balancing act: preventing anti-American sentiments stoked daily on Russian state television from getting out of hand. CNN identified several of the slain Russians on Tuesday; they were portrayed as a mixture of mercenaries and "ultranationalists". However, it is possible that the Russian military was not aware of the attack planned by the Russian contract soldiers acting on orders of the Assad regime.