Bashar al-Assad is bombing Syrian towns with Soviet-made cluster bombs, while rebels are taking down the regime's aircraft with US-made Stinger surface-to-air missiles (SAM), reports say. However, according to official sources, it is not clear who provided the weapons.
"We [Russia] have reliable information that Syrian militants have foreign portable anti-aircraft missile systems, including those made in the USA. Who supplied them must still be determined," Gen Nikolai Makarov told news agency Interfax
The US famously provided Stingers to the mujahedeen in the 1980s during the Soviet invasion of Afghanistan and turning the course of the war.
Makarov's comment partially confirms earlier reports claiming the Free Syrian Army (FSA) has been using shoulder-mounted missiles despite the West outward reluctance in arming the rebellion.
Earlier this week, Syrian rebels said they had shot down an army helicopter and the video of the aircraft spiralling down before exploding was posted on the Internet. Rebels also claimed to have knocked down a fighter in August.
The US stingers are the Rebels' alleged countermeasure to the increasing dropping of Soviet-made cluster bombs on populated areas by the regime, reported by Human Rights Watch.
The New York-based watchdog said it has collected "mounting evidence" showing that Assad's army is using "high explosive, fragmentation, and even improvised "barrel" bombs," on its towns as part of an "intensifying air campaign" against rebel-held areas.
"All of these are Soviet produced weapons they have markings that indicate they were produced in the 1970s' or the early 1980s'. We don't know when they were shipped out of the Soviet Union and if they were shipped directly to Syria ... but there is no question these are weapons produced by the Soviet Union," said Steve Goose, arms director at Human Rights Watch.
Russia is one of the few countries still supporting the Assad regime. Russia and China veto in the UN Security Council blocked several resolutions to impose sanctions on Syria. In the last year Russia has sold to Assad's government $1bn of weapons, the Moscow Times reported.
Russian foreign minister Sergei Lavrov denied that the Syrian government was using "Russian-made" cluster bombs.
"There is no confirmation to this... There are loads of weapons in this region, including in Syria and other countries of the region, and arms are supplied there in large quantities and illegally. It is very difficult to establish from where and how ammunition and weapons are supplied there," Lavrov said.
"[Lavrov] said they were not Russian produced. I guess technically that is correct but they were clearly produced in the Soviet Union and transferred to Syria at some point in time," Goose replied.
Syria denied to even having cluster booms.