Amping up rhetoric against US actions in the area, Russia said Monday it will consider aircraft west of the Euphrates River "air targets" and track them by air and on land.
The Defense Ministry explained the move by saying it will stop abiding by its military cooperation agreement with the US in Syria.
And a top Russian official called the US downing of the Syrian plane an act of aggression that assists terrorists.
A senior US defense official tells CNN the so-called "de-confliction line" remains open with Russia. The official also says the US does not believe Russia is targeting US planes at this time.
This is not the first time that Russia has said the "de-confliction" channel has been suspended. In April, after the US missile strike on a Syrian airbase, Russian Foreign Ministry spokeswoman Maria Zakharova said Russia would suspend the 2015 agreement aimed at minimizing risks of in-flight incidents.
US downing of plane an "act of aggression"
The US military said that it shot down a warplane
that had dropped bombs near Syrian Democratic Force (SDF) fighters. SDF forces are backed by the US-led coalition fighting ISIS.
It's the first time the US has shot down a Syrian aircraft since it began fighting ISIS in the country in 2014.
"This strike can be regarded as another act of defiance of international law by the United States," Russian Deputy Foreign Minister Sergei Ryabkov said Monday, according to Russia's state-run news agency Tass.
"What was it, if not an act of aggression? It was also an act of assistance to those terrorists whom the United States is ostensibly fighting against," Ryabkov said.
"Considered air targets," Russia says
The Russian Ministry of Defense called the downing of the plane "a cynical violation of the sovereignty of the Syrian Arab Republic" and "military aggression." It also demanded an investigation by US command.
Further, the ministry's statement declares that west of the Euphrates River, Russian aircraft will escort any aircraft and unmanned vehicles.
"From now on, in areas where Russian aviation performs combat missions in the skies of Syria, any air-born objects found west of the Euphrates River, including aircraft and unmanned vehicles belonging to the international coalition, tracked by means of Russian land and air anti-aircraft defense, will be considered air targets," the statement reads.
The US military is prohibited by law from coordinating directly with the Russian military, but given the increased pace and scale of military operations in Syria, the US and Russia have sought ways to ensure that their respective personnel are not targeted by mistake, setting up a series of so-called "de-confliction zones" that delineate areas of operation for the coalition and the Russian forces.
Strike followed attack on SDF-controlled area
The Syrian aircraft was destroyed, the Russian ministry said. The pilot of the Syrian Air Force self-ejected over the area controlled by ISIS, and his fate is unknown, the ministry said.
The strike came a little more than two hours after forces allied with the Syrian regime of Bashar al-Assad attacked the north-central Syria town of Ja'Din, which was controlled by the SDF.
A number of SDF forces were wounded in the attack, the statement from the Combined Joint Task Force said. The attack drove the SDF from Ja'Din, which is west of Raqqa, the coalition statement said.
CNN's Mary Ilyushina and Emma Burrows contributed to this report.