Russia, a staunch ally of Syrian President Bashar al-Assad, said it would treat USA -led coalition aircraft flying west of the Euphrates River in Syria as potential targets and track them with missile systems and military aircraft.
"The United States has said its recent actions against Syrian government forces and allied militia have been self-defensive in nature, aimed at stopping attacks on USA -led coalition forces or their local allies.These have included several air strikes against pro-government forces that have sought to advance towards a US military base in southeastern Syria near the border with Iraq, where the USA military has been training rebels to fight IS".
A US strike aircraft shot down a Syrian government fighter jet Sunday shortly after the Syrians bombed USA -backed fighters in northern Syria, the Pentagon said in a statement.
Earlier, the US military confirmed that a US Navy F/A-18 Super Hornet had shot down a Syrian SU-22 on Sunday.
But in April, Russia briefly suspended a hotline meant to prevent midair incidents with the USA over Syria after the American military fired 59 missiles at a Syrian air base following a chemical weapons attack that Washington blamed on the Assad government.
Meanwhile, the US -backed opposition fighters said Assad's forces have been attacking them in the northern province of Raqqa and warned that if such attacks continue, the fighters will take action.
The attack by the Syrian regime caused an unknown number of casualties and drove out SDF fighters, the coalition said, according to NBC News.
In addition to its support for the SDF in Raqqa, coalition forces have been located in At Tanf, on Syria's southern border with Jordan, for more than a year where they have been training local forces.
Russia said its warplanes were flying over Syria at the time of the shootdown and the US failed to use the existing deconfliction channel between USA military officers at al-Udeid air base in Qatar and Russian officers at Hemeimeem air base.
It said the shooting down of the plane was "collective self-defence" and the coalition had contacted Russian counterparts by telephone via an established "de-confliction line to de-escalate the situation and stop the firing".
SDF forces are backed by the US-led coalition fighting ISIS.
On Monday morning, the area where the regime and SDF fighters clashed was quiet, and the US-backed force was continuing to battle IS inside Raqa, the Syrian Observatory for Human Rights monitor said.
Russian Federation is supporting Assad militarily with air power, advisers and special forces as he tries to roll back Islamic State and other militant groups.
The Syrian government this month marched into Raqqa province from the west but had avoided conflict with the USA -backed SDF until the latest incident.
A USA fighter jet shot down a Syrian bomber Sunday, leading to a warning from Russian Federation that "any flying object" will be dealt with as "targets".
Iran's powerful Revolutionary Guard said it launched six Zolfaghar ballistic missiles from the western provinces of Kermanshah and Kurdistan.
The missile attack came amid recent confrontations in Syria between US -backed forces and Iranian-backed pro-government factions.
The Pentagon noted that the U.S. military used a deconfliction channel to communicate with Russia, Syria's main ally, before downing the plane to prevent the incident from escalating.
The most recent was in April when the US fired missiles at a Syrian air base following a chemical weapons attack that Washington blamed on the Assad government.
"I'm also confident that our forces have the capability to take care of themselves", Dunford said.