"First of all, this event is a victory for the Syrian people, the Syrian army, and all those who supported them on the ground – Russia and Iran," Mariani said.
Earlier on Wednesday, US President Donald Trump declared that the United States had defeated the Daesh in Syria, adding that the terrorist group was the only reason that US troops were fighting in the Middle Eastern country during his presidency.
White House spokeswoman Sarah Huckabee Sanders said earlier in the day that US servicemen were returning home from their mission fighting the Daesh terrorist group in Syria.
The US-led coalition of more than 70 countries is conducting military operations against the IS in Syria and Iraq. The coalition's operations in Syria are not authorized by the Syrian government or the UN Security Council.
Daesh (also known as ISIS/ISIL/IS) is a terrorist group banned in Russia.