Beirut - An American fighter jet has for the first time downed a Syrian warplane that Washington accused of attacking US-backed fighters, in a new escalation between the United States and regime forces.

The incident further complicates the country's six-year war and comes as a US-led coalition and allied fighters battle to oust Daesh from its Syrian bastion Raqa.

Government ally Iran also on Sunday launched missiles from its territory against alleged Daesh positions in eastern Syria for the first time, in response to a Daesh-claimed attack in Tehran.

Analysts say neither Washington nor President Bashar Al Assad's regime appear to be seeking further confrontation, but warn that the risks are high in Syria's increasingly crowded battlefields.

The Syrian jet was shot down on Sunday evening after regime forces engaged fighters from the Syrian Democratic Forces (SDF), an alliance battling with US support against Daesh, in an area close to Raqa.

The American F/A-18E Super Hornet shot down the Syrian SU-22 around 7pm as it "dropped bombs near SDF fighters" south of the town of Tabqa, the coalition said in a statement. It said several hours earlier, regime forces had attacked the SDF in another town near Tabqa, wounding several and driving the SDF from the town.

The coalition said the Syrian warplane had been shot down "in accordance with rules of engagement and in collective self-defence of Coalition partnered forces".

Syria's army disputed the account, saying its plane was hit while "conducting a mission against the terrorist group."

It warned of "the grave consequences of this flagrant aggression".

Regime ally Moscow also condemned the downing of the Syrian plane, with deputy foreign minister Sergei Ryabkov saying: "This strike has to be seen as a continuation of America's line to disregard the norms of international law...

What is this if not an act of aggression?"

The incident was the latest skirmish between the US-led coalition and regime forces in the increasingly tense and crowded space in Syria's north and east.

Source: .khaleej Times