Moscow, Syria’s main ally, announced that it would start tracking jets and drones of the US-led coalition and halt an incident-prevention hotline with America, which was set up to avoid accidents in the crowded skies above Syria.

“Any flying objects, including planes and drones of the international coalition, discovered west of the Euphrates river will be tracked as aerial targets by Russia’s air defences on and above ground,” Russian President Vladimir Putin’s defence ministry warned.