"The situation where no facts have leaked the public sphere over nearly half-a-year that the investigation is in progress is simply impossible for the U.S.", Lavrov said. Some estimates place the number of Russian dead at 200.
Russia on Thursday finally recognised that five Russian citizens - not officially affiliated with the Russian military - were likely killed in the strikes in eastern Syria. The wounded were flown to military hospitals in Russian Federation.
According to Fontanka, Wagner is associated with a Russian company Yevro Polis, which has signed a deal with the Syrian government.
The doctor, who works in a Moscow military hospital, said more than 50 wounded men evacuated from Syria were under treatment at the hospital last Saturday.
Yevgeny Prigozhin, a Russian businessman with ties to Russian President Vladimir Putin, is accused of funding the Internet Research Agency.
USA forces are "focused on" fighting Islamic State (IS) militants, he said, adding: "We're not looking for a fight with anyone else, but as Secretary Mattis said last week: 'If you threaten us, it will be your longest, and your worst, day'".
Last week saw mercenaries fighting on two very different battlefields, one in Syria, the other virtual. More than 13.1 million Syrians are in need of humanitarian aid, including 6.1 million who have been displaced within the country during the almost seven-year war, according to the United Nations.
"They help Russian Federation obfuscate Russia's role in Syria", Matti Suomenaro, a researcher for the Institute for the Study of War told me this week.
For a cynic like Putin, whose air force has bombed other enclaves of USA -supported rebels in Syria, the inability of the U.S.to stop a North Atlantic Treaty Organisation ally, Turkey, from attacking another ally in Afrin is a sign of weakness.
Finally, there is the strategic argument for why Russian Federation would participate in the attack at Deir Ezzor.
"I would not say that we were hostage to some expectations". While the USA has attempted to end the Turkish assault through diplomacy, it has not offered to protect Kurdish fighters aligned with the People's Protection Group, or YPG, who remain in the city. When Mattis and other USA officials publicly discuss the US mission in Syria, they say only that it is to fight the Islamic State.
Some said the offensive was launched because of a rumored relocation of some fighters from there to the Kurdish enclave of Afrin in northwestern Syria, which is facing a Turkish offensive. The YPG are key USA partners in the campaign against the Islamic State.