Russia on Monday said it will treat U.S. or coalition aircraft that fly over any of its operating areas in western Syria as targets, after a U.S. F/A-18 Super Hornet downed a Syrian bomber a day earlier.

"Any aircraft, including planes and drones of the international coalition, detected in the operation areas west of the Euphrates River by the Russian air forces will be followed by Russian ground-based air defense and air defense aircraft as air targets," according to a Russian Defense Ministry statement.

Russia called the downing of a Syrian Air Force Su-22 jet a "cynical violation of Syria' sovereignty."

"The US' repeated combat operations under the guise of ‘combating terrorism' against the legitimate armed forces of a U.N. member-state are a flagrant violation of international law, in addition to being actual military aggression against the Syrian Arab Republic," the ministry added.

Syrian aircraft on Sunday attacked U.S.-backed Syrian Democratic Forces.

The attack wounded a number of Syrian Democratic Forces fighters and drove the group from the town. The bombing drew the attention of coalition aircraft, which "conducted a show of force and stopped the initial pro-regime advance toward the SDF-controlled town."

After the attack, coalition officials contacted Russian officials on an established "de-confliction line" to try to calm the situation.

However, at 6:43 p.m. Syrian time, a Syrian regime Su-22 plane began dropping bombs near Syrian Democratic Forces fighters south of Tabqah.

"In accordance with rules of engagement and in collective self-defense of Coalition partnered forces, [the Syrian plane] was immediately shot down by a U.S. F/A-18E Super Hornet," the statement read.

As of Monday morning Washington time, the status of the Syrian pilot was unknown. The Russian Embassy in the U.S. said he ejected into territory controlled by the Islamic State.

In the Tass report Monday, the Russian Defense Ministry said it was shutting down the line of communication, which is used to ensure Russian and coalition forces fighting ISIS don't accidentally bomb each other.

"As of June 19 this year, the Defense Ministry of the Russian Federation has ended its interaction with the US side under a memorandum for preventing incidents and providing for safe flights during operations in Syria and demands that the US command carry out a careful investigation and report about its results and the measures taken," the statement said.