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.
"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.