As reported by Reuters on Thursday, the Syrian military has started using new types of air and ground weapons supplied by Russia.
The weapons are described by a source in the Syrian army as "highly accurate and effective, and hit targets precisely."
The source declined to give further details about the weapons.
Earlier U.S. officials said the United States had identified a small number of Russian helicopters at a Syrian airfield, although it was not clear when the Russian helicopters had arrived there.
The U.S. and NATO have raised concerns over Russia's military buildup in Syria.
Moscow is also expanding its own forces on the ground in Syria, where more than four years of war have killed an estimated 250,000 people.
The Syrian government faces a manpower problem in the army and has lost ground this year in the northwest, the southwest and the center of the country to an array of groups including Islamic State and other insurgents battling to topple President Bashar al-Assad.
According to U.S. officials' assessments, Russia has sent about 200 naval infantry forces, battle tanks, artillery and other equipment to an airfield near Latakia. About two military cargo flights land to an air base at Latakia daily, U.S. officials say.
Thus far in the conflict, Iran and its Lebanese ally Hezbollah have been the main source of military support for Damascus. Hezbollah has deployed directly in combat, while Iran has mobilized militias and sent military advisers.
Syrian officials say the Russian military presence is limited to experts.