Ambassador Vassily Nebenzia told reporters that he protested the assault in Syria's eastern province of Deir Ezzor during a closed-door Security Council meeting.
"It was inadmissible for whatever reasons it was justified," Nebenzia told reporters, adding that he told the US "to remember that they are in Syria illegally in fact. They were not invited there.
"They claim all the time that they fight international terrorism, but we see that it goes beyond that. To confront those who really fight international terrorism on the ground in Syria is criminal."
READ: Terrified children, empty streets in Syria's Afrin as Turkey attacks
The US said the international coalition carried out air strikes against pro-government fighters on Wednesday to defend its allies in Deir Ezzor.
It accused Syrian pro-government forces of initiating an attack on the US-backed Syrian Democratic Forces (SDF).
The Syrian government complained in a letter to UN Secretary-General Antonio Guterres that the attack "represents a war crime and a crime against humanity".
The US-led coalition was established in 2014 to fight the Islamic State group in Syria and Iraq, but it has bombed troops loyal to Damascus on several occasions.
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