Satellite photos obtained by a leading defense research group suggest that Syria may be preparing to receive Russian troops, as the country remains mired in a civil war that has killed an estimated 250,000 people and displaced millions more.

IHS Jane's said Tuesday that the images, taken in mid-September, reveal the construction of two additional military facilities near Syria's Mediterranean coast. The defense intelligence group acquired the imagery from a commercial satellite division of Airbus Group.

Rob Munks, editor of IHS Jane's Intelligence Review, said Tuesday the previously undisclosed work was taking place at a weapons storage facility and military base north of the coastal city of Latakia, suggesting that Russia could potentially deliver troops to both locations.

Syria "may be preparing to receive Russian forces," Munks said.

Munks also noted a "substantial increase" in jets at Latakia airport, saying it indicated "rapid build-up of Russia's expeditionary force."

"With a significantly enhanced ground-attack capability, this represents a substantial step-change in Russia's combat ability."

Russia has been rapidly increasing its military presence at an air base south of Latakia, a stronghold of Syrian President Bashar al-Assad. Moscow has positioned combat planes and helicopters there in addition to tanks and housing blocks.

The US has expressed concern over Russia's support for Assad and views a strengthening of military ties between Moscow and Damascus as troubling, even as both the US and Russia attempt to cooperate in the fight against the "Islamic State" (IS) group.

A senior Syrian military official told news agency AFP that Damascus had received new weaponry, including at least five fighter jets. He said Syria had also received "sophisticated military equipment to fight IS," including targeting equipment and precision-guided missiles.

Russia has been a staunch supporter of Damascus since Soviet times, and President Vladimir Putin says his nation's support of Assad is in line with international law. The US says any military backing for the Syrian regime would draw more extremists to the country and could delay any prospect of peace.

bw/cmk (AFP, Reuters, AP)