President Vladimir Putin ordered the Russian military in Syria to destroy any threatening targets, the Interfax news agency reported Friday.
"I order you to act as tough as possible. Any target that poses a threat to Russian [military] grouping or ground infrastructure has to be destroyed immediately," Putin said at a Defense Ministry meeting.
He said that his order was a warning to anyone who would try to provoke the Russian military.
Putin's order was given amid media reports of an expanding Russian military presence in Syria.
On Thursday, the Britain-based Syrian Observatory for Human Rights reported that the Russian air force was preparing to use two Syrian airbases near Homs to strike targets in the Islamic State-controlled city of Palmyra.
Russian Defense Ministry officials have been repeatedly denying such reports, saying there is no "operational logic" in using additional airbases in Syria.
Since Russia's air campaign began on Sept. 30, Russia has also been using an airbase in Latakia, in the northwest, to strike targets in northern Syria.
In response to Turkey's downing of a Russian Su-24 fighter-bomber on the Turkish-Syrian border, Moscow had increased its air defenses in Syria, including the deployment of S-400 systems to the Latakia airbase.
Islamic State is a terrorist group banned in Russia.