Unconfirmed reports suggesting that Russia is planning to expand its military support for embattled President Bashar Assad have prompted a warning from the United States that such actions could lead to a confrontation with coalition forces in Syria.

The State Department issued a statement Saturday after Secretary of State John Kerry called Russian Foreign Minister Sergey Lavrov to express concern over unconfirmed reports "suggesting an imminent enhanced Russian military buildup" in Syria.

While not elaborating on or confirming the accuracy of those reports, the State Department said Kerry made clear to Lavrov that such actions "could further escalate the conflict, lead to greater loss of innocent life, increase refugee flows and risk confrontation" with the anti-Islamic State coalition led by the U.S.

Russia has been a stalwart ally of Assad throughout Syria's civil war and has provided diplomatic support and weaponry to help the Syrian leader maintain his grip on power. Moscow also maintains a small naval facility at the Syrian port of Tartous on the Mediterranean Sea.

In another development, anti-government violence erupted Saturday in a southern Syrian province that had largely stayed on the sidelines of the country's civil war.

The violence in Sweida province, a stronghold of the Druze minority sect, followed the killing of a prominent cleric in rare explosions Friday that claimed the lives of at least 25 others, activists and pro-government media said.

Concerns about Russia in Syria2:03

Statue destroyed

Rioters holding the government responsible for the cleric's death destroyed the statue of late Syrian President Hafez Assad and besieged security offices, the Britain-based Syrian Observatory for Human Rights and other activist groups said.

Balous, who was a strong supporter of rebels trying to topple Assad, died in one of two consecutive car bomb explosions, including one near the National Hospital in Sweida.

The Observatory said the death toll rose Saturday to 37, including six security personnel killed in clashes with rioters. The city had witnessed large rallies in the days before the explosions against the failure of the government to provide basic services. Activists reported that there was no Internet service for the past few days.

Syria's official news agency and other activist groups put the death toll from the blasts at 26. There was no immediate claim of responsibly for the bombings.