Russia's defence ministry says it will treat US-led coalition planes in Syria, west of the Euphrates River, as targets after the US military shot down a Syrian Air Force jet on Sunday (18 June).
Moscow has condemned the US downing of the Syrian government fighter jet after it dropped bombs nears US partner forces.
The Russian defence ministry says in a statement that, starting Monday, it will track all jets and drones of the US-led coalition west of the Euphrates and treat them as targets.
The ministry also called on the US military to provide a full account of why it decided to shoot down the Syrian SU-22.
Russia, a key backer of Syrian President Bashar Assad, has been providing an air cover to the government's offensive on Isis since 2015.
Russian Deputy Foreign Minister Sergei Ryabkov told Russian news agencies on Monday that the downing was akin to "helping the terrorists that the US is fighting against".
Ryabkov asks: "What is this, if not an act of aggression?"