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

In Washington, the State Department issued a statement after U.S. Secretary of State John Kerry called Russian Foreign Minister Sergey Lavrov to express concern over unconfirmed reports “suggesting an imminent enhanced Russian military build-up” 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 operating led by the U.S. that is carrying out strikes in Syria.