The Russian Foreign Ministry says that five Russians who were not military personnel may have been killed in a clash with U.S.-led forces in Syria last week and claims that reports putting the Russian death toll in the dozens or hundreds were "disinformation."
Foreign Ministry spokeswoman Maria Zakharova's remarks on February 15 marked the first time a Russian official has directly acknowledged that Russian citizens may have been killed in an incident that occurred in the Deir al-Zor province on February 7.
"According to preliminary information, we could be talking about the deaths of five people -- presumably Russian citizens -- as a result of an armed confrontation whose causes are being examined," Zakharova told a regular news briefing.
"Reports about the deaths of dozens or hundreds of citizens are classic disinformation," she said. "There were not 400, not 200, not 1,000, and not 10."
Associates of Russian mercenaries fighting alongside Syrian government forces have said there were large-scale casualties among the contractors in the clash.
The U.S. Defense Department has said air strikes launched after as many as 500 pro-government forces attacked a base housing opposition forces and U.S. military advisers killed about 100 of the attackers.
In recent days, news reports, open-source researchers, and relatives and colleagues of Russian mercenary soldiers have said that multiple Russians -- possibly dozens or more -- may have died in the exchange on February 7.
The Reuters news agency, citing three sources familiar with the matter, said about 300 men working for a "Kremlin-linked private military firm" were either killed or injured in Syria last week.
It cited a Russian military doctor as putting the death toll at 100 men, while a source who knows several of the fighters claimed at least 80 had been killed.
The military doctor works at a Moscow military hospital and was directly involved in the treatment of wounded men evacuated from Syria, the report said. The physician said there were more than 50 patients currently being treated, with 30 seriously injured.
The sources did not specifically tie the casualties to the U.S.-led counterattack, but the timing generally coincided with the February 7 incident.
When asked about the Reuters report, a Kremlin spokesman said he had nothing to add to previous statements.
More than 40 Russian military personnel have died in Syria since Moscow launched a campaign of air strikes in September 2015 in support of President Bashar al-Assad's regime.
The support has helped Assad avoid collapse amid a devastating civil war, which started in 2011 with a crackdown on pro-democracy demonstrators.
It has also ratcheted up tensions with the United States, which has backed rebel groups -- including the Syrian Democratic Forces (SDF), an alliance of Syrian Arab and Kurdish fighters -- fighting to topple Assad.
An SDF base near the Euphrates River "deconfliction line" set to avoid clashes between the two sides in Deir al-Zor Province was the site of the February 7 incident.
The Pentagon said coalition advisers had been with SDF forces when the base was assaulted and said its actions against the attackers were in "self-defense."
Russian President Vladimir Putin in December ordered a partial withdrawal of most of the 48,000 Russian military personnel from Syria, but also signed a law ratifying an agreement enabling Russia to expand operations at its naval facility in Tartus.
Kremlin spokesman Dmitry Peskov has acknowledged that some Russian citizens could also be in Syria but that Moscow does not have any information about them.
Western officials have said some Russian private contractors in Syria could be involved in attempting to secure oil assets on behalf of the Assad regime, particularly in energy-rich Deir al-Zor Province.
With reporting by Reuters and Meduza