Russia's announcement it is deploying its most hi-tech air defense system to its base in Syria is raising "significant concerns" for the US military, a US official said Wednesday.

Russia says it is sending S-400 anti-aircraft missiles to Latakia in northwestern Syria, in a move that comes after Turkey shot down a Russian fighter jet in the increasingly crowded air space along the border on Tuesday, AFP reports.

The S-400 missiles have a range of about 400 kilometers (250 miles), posing a potential threat to US-led coalition planes, and adding yet another dangerous element to an already volatile mix of competing military interests in Syria.

"It's a capable weapons system that poses a significant threat to anyone," a US official speaking on condition of anonymity told AFP. "There are significant concerns related to air operations in Syria."