WASHINGTON -- Secretary of State John Kerry expressed U.S. concern over reports of Russia's enhanced military buildup in Syria in a phone call Saturday with his Russian counterpart, the State Department said. "The secretary made clear that if such reports were accurate, these actions could further escalate the conflict, lead to greater loss of innocent life, increase refugee flows and risk confrontation with the anti-ISIL coalition operating in Syria," the department said, using an acronym for the Islamic State group.

It said Kerry and Russian Foreign Minister Sergei Lavrov agreed that discussions on the Syrian conflict would continue in New York this month when the United Nations General Assembly meets there.

Media reports Friday quoted U.S. officials as describing an increase in Russian military activity in Syria, expanding Moscow's support for Syrian President Bashar Assad amid the grinding civil war.

Quoting unidentified Obama administration officials, the New York Times reported Russia has dispatched a military advance team to Syria and has sent prefabricated housing units for hundreds of people to a Syrian airfield and delivered a portable air-traffic-control station there.

Some U.S. officials said the temporary housing suggested Russia could deploy as many as 1,000 advisers or other military personnel to the airfield that serves Latakia, Syria’s principal port city that is near the Assad family's ancestral home, the Times reported. It said officials see no indications Russia intends to deploy significant ground forces, but may be preparing the airfield as a base for transporting military supplies or a launching pad for air strikes supporting Assad.

The Los Angeles Times reported U.S. intelligence has gathered evidence of possible military housing from satellite reconnaissance photos.

A 2011 uprising against four decades of Assad family rule turned into a full-blown civil war.

Lavrov said last month the U.S. should cooperate with Assad, a longtime Moscow ally, to fight Islamic State group forces who have seized parts of northern and eastern Syria.

The U.S. and Russia have been at loggerheads over Syria. Russia has backed Assad, while the U.S. advocates a political transition to end his rule.

A U.S. security source told Reuters there are signs of a Russian move to intervene beyond the robust support of the last few years, but did not elaborate. The source said the U.S. will be watching to see whether any increased Russian might in Syria will be used to push back the Islamic State group or to bolster Assad.

(Reporting by Will Dunham, Doina Chiacu and Mark Hosenball; Editing by Mohammad Zargham)