Russian Deputy Foreign Minister Sergey Ryabkov has strongly condemned the United States for shooting down a Syrian Air Force fighter jet in Syria's militant-held northern province of Raqqah as a “massive violation of international law and de facto military aggression.”

“This strike has to be seen as a continuation of America's line to disregard the norms of international law,” Ryabkov told the state-owned TASS news agency in Moscow on Monday.

He added, “What is this if not an act of aggression? It is, if you like, help to those terrorists that the US is ostensibly fighting against, declaring they are carrying out an anti-terrorism policy.”

Ryabkov’s remarks came a day after the Syrian army said that the US-led coalition purportedly fighting the Daesh Takfiri terrorist group had targeted one of its Sukhoi Su-22 warplanes over al-Rasafa area in the southern countryside of Raqqah Province.

The Syrian General Command of the Army and Armed Forces announced in a statement that the military aircraft was on a combat mission against Daesh terrorists, noting that the pilot of the jet had gone missing after the “flagrant aggression.”

In return, the US-led Combined Joint Task Force said in a statement that pro-government Syrian forces had attacked the so-called Syrian Democratic Forces (SDF) in the town of Ja'Din south of Tabqa, wounding a number of the US-backed militiamen and driving the rest from the town.

Meanwhile, the Russian Defense Ministry has terminated its use of a military hotline for avoiding incidents in Syrian airspace, stating that it will now track all coalition flights west of the Euphrates River.

"The command of the coalition forces did not use the established communication channel for preventing incidents in Syrian airspace,” the Russian ministry’s statement read.

It added, “As a result, it now ends cooperation with the American side from June 19 based on a memorandum for prevention of incidents and ensuring safety of air flights during operations in Syria, and demands a careful investigation by the US command of the downing.”

“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 defenses on and above ground,” the statement pointed out.

On April 7, US warships in the eastern Mediterranean launched a barrage of 59 Tomahawk missiles against Shayrat Air Base in Syria’s Homs Province, which Washington alleged was the origin of a suspected chemical attack on the town of Khan Shaykhun in Syria’s Idlib Province earlier that month.

Washington has so far failed to provide any evidence to support the accusations, prompting criticisms from many countries and international intuitions for choosing to take unilateral military action hastily and without proof.

The strike drew the praise from anti-Damascus militant groups as well as the countries long viewed as their staunch supporters, including Saudi Arabia, Israel and Turkey.

Syria has categorically denied carrying out the purported gas attack, with Foreign Minister Walid al-Muallem stressing that the Idlib airstrike had targeted a depot, where terrorists stored chemical weapons.