Turkish-backed Syrian rebel fighters stand guard at a checkpoint in the Syrian town of Azaz on a road leading to Afrin, on February 1, 2018. (AFP PHOTO)

MOSCOW, Feb. 15 (Xinhua) -- Russian Foreign Ministry spokeswoman Maria Zakharova said Thursday that five Russian nationals were preliminarily confirmed to have been killed in Syria in clashes with the U.S.-led coalition last week.

"According to preliminary data, as a result of the armed conflict, the causes of which are being clarified, and five people, presumably Russian citizens, could have been killed," Zakharova said in a briefing.

She said that others were injured, but details of their nationalities are being checked.

The spokeswoman underlined that reports about large-scale casualties among the Russian troops are a "classic disinformation."

"I want to stress once again, they were not Russian servicemen," Zakharova said, adding that there were many people of various nationalities with different purposes in Syria's conflict zones and that it was hard to trace all of them.

Last week, the Russian Defense Ministry said a pro-government militia unit conducted a reconnaissance and search operation on Feb. 7 in the vicinity of an oil refinery in the province of Deir al-Zour to identify and destroy a bandit group responsible for shelling government troop positions, and yet came under fire of the U.S.-led coalition and its local allies.

The coalition claimed that it carried out airstrikes against "Syrian pro-regime forces" that launched an "unprovoked attack" on Kurdish-led Syrian Democratic Forces' headquarters and killed an estimated 100 militiamen.

It is the first time that Moscow officially admitted that Russian citizens were killed in a clash with the U.S.-led coalition in Syria.