US F/A-18
An F/A-18E Super Hornet takes off from the flight deck of the US Navy aircraft carrier USS Nimitz on 29 October 2016US Navy/Seaman Weston A. Mohr/Handout/File Photo via REUTERS.

A US strike aircraft shot down a Syrian regime fighter jet on Sunday (18 June), the Pentagon said. The downing of the government aircraft came shortly after Syrian forces bombed US-backed Syrian Democratic Forces (SDF) in the village of Ja'Din, southwest of Raqqa.

The incident marks the fourth time within a month that the US military has attacked pro-Syrian government forces, The Washington Post reported. It is also the first time the US has shot down a manned hostile aircraft in more than 10 years.

The Syrian military said the aircraft's pilot was killed in the attack and that the jet was carrying out a mission against Isis at the time of the downing.

"The attack stresses coordination between the US and Isis, and it reveals the evil intentions of the US in administrating terrorism and investing it to pass the US-Zionist project in the region," the Syrian military said in the statement.

The Pentagon noted that the US military used a deconfliction channel to communicate with Russia, Syria's main ally, before downing the plane to prevent the incident from escalating. US-led aircraft ended the fighting by flying close to the ground at a low speed in what is referred to as a "show of force".

Despite the calls to stand down and the US presence, the Syrian Su-22 jet dropped an unknown number of munitions on the SDF. US Central Command spokesman Col John Thomas said the Syrian jet arrived with little warning, The Post reported. US forces in the area were not directly threatened, he added.

Thomas said that a nearby US aircraft attempted to hail the Syrian aircraft after the bombing. After hailing attempts failed, a US F/A-18 shot down the Syrian jet "in accordance with rules of engagement and in collective self-defence of coalition partnered forces," the Pentagon said.

According to the Post, Thomas rejected the Syrian military's claim that the aircraft was bombing Isis, noting that Ja'Din is under the control of SDF and that Isis has not been in the area for some time.

The attack by the Syrian regime caused an unknown number of casualties and drove out SDF fighters, the coalition said, according to NBC News. "The Coalition's mission is to defeat Isis in Iraq and Syria," a statement from the coalition 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 SDF, which is comprised of Syrian Kurds and other Arab fighters, is considered by the US to be an important ally in the fight against Isis.