The Russian Foreign Ministry says that "several dozen" citizens of Russia and other former Soviet republics who are not members of the military were wounded in a recent battle with U.S.-led forces in Syria.

The Foreign Ministry statement on February 20 was Moscow's first formal acknowledgement that Russian mercenaries suffered heavy casualties in a lopsided clash in Syria's Deir-al-Zor on February 7.

The statement gave no new figure for the number of Russians killed in the incident, which Foreign Ministry spokeswoman Maria Zakharova said on February 15 was about five -- far fewer than some reports have suggested.

The United States has said that air and artillery strikes launched after as many as 500 pro-government forces attacked a base housing U.S.-backed opposition forces and U.S. military advisers killed about 100 of the attackers.

In recent days, media outlets, open-source researchers, and relatives and colleagues of Russian mercenary soldiers have said that many Russians -- possibly dozens or hundreds -- may have died in the exchange.

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.

"In the course of a recent military confrontation...there were deaths [among] citizens of Russia and countries of the CIS...and there were wounded -- several dozens of them," the new statement said.

It said that "servicemen of the Russian Federation in no way took part" in the clash, and that no Defense Ministry weapons or vehicles were not used.

The CIS is the Commonwealth of Independent States, which includes 11 former Soviet republics.

Russia has given President Bashar al-Assad's government crucial support throughout the 7-year-old war in Syria, which began with a government crackdown on protests.

Moscow helped turn the tide of the conflict in Assad's favor by a launching a campaign of air strikes in 2015 and stepping up its military presence on the ground.

The United States has backed rebel groups -- including the Syrian Democratic Forces (SDF), an alliance of Syrian Arab and Kurdish fighters -- fighting to topple Assad.