Russia has acknowledged that the country has military advisers in Syria amid widening friction with western countries over Moscow's backing for Syrian President Bashar al-Assad.
According to The Washington Post, the extent to which Russia is supporting Syria has recently come to the fore as unprecedented numbers of Syrian refugees and others from the region stream into Europe.
This week, the United States urged Greece and Bulgaria to reject overflight requests for Russian aircraft, fearing that Moscow seeks to increase its arms shipments to Assad's forces.
Russia's Foreign Ministry called Washington's intervention "international boorishness" in a statement Wednesday, saying Moscow only seeks to help the Syrian government fight terrorists.
