Satellite photos taken in mid-September and obtained by IHS Jane's show Russian forces developing two additional military facilities near Syria's Mediterranean coast, Rob Munks, editor of IHS Jane's Intelligence Review, said on Tuesday.
Munks said the previously undisclosed work was taking place at a weapons storage facility and a military base north of Latakia, suggesting Russia is preparing to place troops at both locations.
Russia has been dramatically increasing its forces at an air base south of Latakia. The coastal province of Latakia is a stronghold of Syrian President Bashar al-Assad, whose forces have encountered a series of military setbacks in 2015 and have professed military "fatigue."
Russia has backed Assad since the Syrian civil war began in 2011, not only through military support but also through diplomatic cover at the United Nations Security Council, where Moscow wields a veto as a permanent member.
The rise of the Islamic State in Syria and the Levant (ISIL) over the last year has worried both Russia and the United States, but Washington’s international coalition to strike ISIL has come in spite of Assad, whose removal remains a U.S. foreign policy objective and a point of contention with Moscow.
Jane's, a defense intelligence provider, acquired the images from a commercial satellite division of Airbus Group SE, according to the Wall Street Journal, which first reported on the imagery.
Munks told Reuters one of the sites was located about 4 miles north of Latakia and the second was 2 miles west of that. The images showed construction of new buildings and grading of terrain, as well as the presence of new tents typically used by Russian military units. One of the facilities is adjacent to a surface-to-air missile site, Munks added.
Separately on Tuesday, Secretary of State John Kerry said that the Obama administration hopes Russia will play a positive role in Syria and back a political transition for the country to end the current conflict and blunt ISIL.
Kerry said that Russia's military buildup in Syria appears initially intended to protect its existing assets and personnel on the ground, but he said that Moscow's ultimate aim in Syria is not yet clear.
Last Friday, the U.S. announced that Washington and Moscow would hold direct talks about Syria, a signal that the rivals could be seeking some compromise in their differing approaches to the country's civil war.
Al Jazeera and wire services