U.S.-backed coalition forces shot down a pro-Syrian regime fighter jet on Sunday after it bombed the Syrian Democratic Forces-held town of Ja-Din, the coalition said.
An initial attack by forces loyal to Syrian President Bashar al-Assad occurred at 4:30 p.m. local time (9:30 a.m. ET), causing an unknown number of casualties and driving out SDF fighters, the coalition said in a statement.
About two hours later, a Syrian jet dropped bombs and was "immediately" shot down by a U.S. war plane, the coalition said.
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"The Coalition's mission is to defeat ISIS in Iraq and Syria," the statement said. "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."
The United States considers the SDF — which is largely composed of Syrian Kurds but also includes ethnic Assyrians, Turkmen and Armenians — an important ally in its fight against ISIS.
The bombing signaled the latest escalation between coalition and pro-Assad forces.
On May 18, a coalition airstrike appeared to mark the first direct targeting of pro-regime soldiers. About a month earlier, the United States fired cruise missiles at a Syrian military airfield after a regime-led chemical attack, although the strike was timed to avoid casualties.
The Syrian army said Sunday in a statement that the fighter jet crashed and its pilot is missing, Reuters reported.
The statement described the Syrian military advance as a combat mission against ISIS militants, according to Reuters, and it said the confrontation with coalition forces was a "flagrant" attack designed to undermine the army.