The incident came as a monitoring group reported the first ground fighting between Syrian regime troops and the US-backed alliance of Kurdish and Arab fighters.
"At 6:43 pm (local time), a Syrian regime SU-22 dropped bombs near SDF (Syrian Democratic Forces) fighters south of Tabqah and, in accordance with rules of engagement and in collective self-defence of Coalition partnered forces, was immediately shot down by a US F/A-18E Super Hornet," the Combined Joint Task Force said in a statement.
It said that two hours earlier, forces loyal to President Bashar al-Assad attacked SDF fighters in the town of Ja'Din south of Tabqah, "wounding a number of SDF fighters and driving the SDF from the town."
Coalition aircraft then stopped the pro-regime forces' initial advance with a "show of force," the coalition added.
The Combined Joint Task Force stressed that the coalition's mission is to defeat IS.
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"The Coalition does not seek to fight Syrian regime, Russian, or pro-regime forces partnered with them, but will not hesitate to defend Coalition or partner forces from any threat," it said.
"The demonstrated hostile intent and actions of pro-regime forces toward Coalition and partner forces in Syria conducting legitimate counter-ISIS operations will not be tolerated."
Following the downing of the Syrian plane, clashes between regime troops and coalition-backed fighters broke out in two villages some 25 miles (40 kilometres) south of the city of Raqa, the Syrian Observatory for Human Rights said.

