Russia is sending two navy ships and a unit of marines to Syria to protect Russian citizens and a naval base there, according to Interfax News Agency.
The amphibious landing vessels, each capable of carrying 300 marines and 12 tanks, will sail for the Syrian port of Tartus.
"We must protect our citizens," Interfax quoted Russian Air Force Maj.-Gen. Vladimir Gradusov. "We won't abandon the Russians and will evacuate them from the conflict zone, if necessary."
Observers say the move reveals Russia's concern about the growing intensity of the civil war and the future of Syrian President Bashar Assad.
Russia, Syria's most important ally, has shipped weapons to the Assad regime and blocked international efforts to impose sanctions.