Russia has started flying drone aircraft on surveillance missions in Syria, two U.S. officials said on Monday, in what appeared to be Moscow's first military air operations inside the country since staging a rapid buildup at a Syrian air base.
The U.S. officials, who spoke to Reuters on condition of anonymity, could not immediately say how many Russian drones were involved in the surveillance missions or the scope of the flights.
The Pentagon declined to comment.
The start of Russian drone flights underscored the risks of U.S.-led coalition aircraft and Russian flights operating in Syria's limited airspace.
U.S. and Russian defense chiefs agreed on Friday to explore ways to avoid accidental interactions, also known as "deconfliction" in military parlance.
The discussions may gain added urgency, now that Moscow has started drone flights.
The former Cold War foes have a common adversary in Islamic State militants in Syria, even as Washington opposes Moscow's support for Syrian President Bashar al-Assad, seeing him as a driving force in the nation's devastating, 4 1/2 year civil war.
But Russia may also want to target opposition fighters that the United States supports in Syria, seeing them as equal threats to Assad.
Russia's drone operations appeared to be staged out of an air base near Latakia, where it has moved heavy military equipment, including fighter jets, helicopter gunships and naval infantry forces in recent days, U.S. officials said.