Russian media also cited unconfirmed claims that overall casualties could have been as high as 200 and Russians could have accounted for the bulk of them. Russia's military said it had nothing to do with the attack and the US accepted the claim. The US is going along with that, although defense chief James Mattis called the entire situation "perplexing".
Kremlin spokesman Dmitry Peskov refrained from comment, saying on Tuesday that the reports needed to be verified.
Neither the Kremlin nor the Russian Ministry of Defense talks about private military contractors in Syria.
Ionov said not all those killed were Russian, and that some were from other parts of the former Soviet Union. "But Russia will pretend nothing happened".
PA A Challenger 2 tank passes a pair of Warrior tracked armoured vehicles
The mercenaries are said to have been hired by private military firms backing Syrian pro-government troops.
As the Islamic State's dominance in the region has been decimated, state actors have entered the fill the power vacuum.
Bloomberg has also identified the mercenary outfit involved in the attack.
The T-72 tank came from the "same hostile forces" which attacked US special operations troops and allied Syrian fighters last Wednesday in eastern Syria, officials said.
It also quoted Alexander Averin, leader of extreme leftist group Another Russia, as saying that one of its activists, Kirill Ananyev, was killed by the US strike near Khusham.
It was a long time coming, Rohit on his match-winning ton
Rohit Sharma finally shrugged off his poor run in South Africa with a match-winning century in Port Elizabeth on Tuesday. Last year, Rohit dedicated his third double century to Ritika on the occasion of their second marriage anniversary.
According to the above named reports, the Russian military were among Syrian forces targeted coalition of Hasama.
At no point, an American military spokesman said, was there any chance of direct conflict between United States and Russian forces. It also quoted Alexander Averin, the leader of extreme leftist group Another Russia, saying that one of its activists, Kirill Ananyev, was killed by the USA strike near Khusham, where the US said its counterattack occurred. "(...) You can't ask Russian Federation to prevent the conflict in the case when she is not in control, it could not be done", said Mattis.
"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 fighters had no air cover or mobile air defense to protect them during the fighting, they said.
Russian opposition politician Grigory Yavlinsky, urged Mr Putin to come clean to using mercenaries to defend Syrian president Bashar-al-Assad.
Russia plans to help Syria rebuild energy facilities that have been devastated by years of war, Russian Energy Minister Aleksandr Novak has said.
CIA denies report it was conned by Russian who promised Trump info
Trump has also said he believes Russian President Vladimir Putin when he denies Russian interference in the election. The Russian was told by the Americans to leave Western Europe and not return, according to the Times .
The general pressed the points that US forces are focused on ISIS in Syria, they were not "looking for a fight", and the deadly strikes were ordered in self-defense.
The death toll from the skirmish, already about five times more than Russia's official losses in Syria, is still rising, according to one mercenary commander who said by phone that dozens of his wounded men are still being treated at military hospitals in St. Petersburg and Moscow.
The US Air Force Central Command released a video on Tuesday, showing an airstrike on Syrian government forces in the province of Deir ez-Zor.
Benitez: I'd rather Newcastle beat relegation rivals than Man Utd
United beat the Magpies easily (4-1) back in November at Old Trafford, and Benitez will be determined to get revenge at St. "I don't think he has been the same player since he did his hamstring earlier in the season".