A specialist defense publication says satellite photos taken in mid-September show Russian forces developing two additional military facilities near Syria's Mediterranean coast.
The editor of IHS Jane's Intelligence Review, Rob Munks, said on September 22 that the previously undisclosed work was taking place at a weapons storage facility and a military base near Latakia airport, suggesting Russia is preparing to place troops at both locations.
He said the images showed construction of new buildings and grading of terrain, as well as the presence of new tents used by Russian military units.
Munks also noted a "substantial increase" in jets at Latakia airport, saying it pointed to a "rapid buildup of Russia's expeditionary force."
"With a significantly enhanced ground-attack capability, this represents a substantial step-change in Russia's combat ability," he added.
Russia, a staunch ally of Syrian President Bashar al-Assad, has sent fighter jets, helicopters, tanks, artillery, antiaircraft missiles, and troops to Latakia Province, Assad's stronghold.