The US reportedly killed more than 100 Russian and Syrian-backed fighters in a 3-hour military blitz

US Marine Corps

US Marines firing a howitzer in Syria

• US-led coalition in Syria killed more than 100 Syrian regime forces on Wednesday in response to an attack on one of its bases.
• Syrian regime forces' initial coordinated attack included tanks, howitzers and more, but only one US-backed SDF fighter was injured.
• Regime forces were likely attempting to take an oilfield near Khusham.

The US-led coalition in Syria killed more than 100 Syrian regime forces on Wednesday after its headquarters suffered an "unprovoked attack," according to a statement from Operation Inherent Resolve and Reuters.

Syrian regime forces launched a coordinated attack that included about 500 regime troops, 122mm howitzers, tanks and multiple launch rocket systems on the US-backed SDF headquarters in Deir al-Zor province approximately five miles east of the Euphrates River.

The river acts as a de-confliction line between the coalition and Russian and Syrian forces.

Regime forces operating Russian-made T-55 and T-72 tanks fired 20-30 tank rounds within 500 feet of the SDF base, where some US troops were embedded, according to Pentagon press secretary Dana W. White.

One SDF fighter was injured, Reuters reported.

The US-led coalition responded with "AC-130 gunships, F-15s, F-22s, Army Apache helicopter gunships and Marine Corps artillery," according to Fox News reporter Lucas Tomlinson. CNN also reported that HIMARS and MQ-9 drones were used in the attack.

US Marine Corps

US Marines firing a howitzer in Syria.

"Along with ground based fire support, these aircraft released multiple precision fire munitions and conducted strafing runs against the aggressor force, stopping their advance and destroying multiple artillery pieces and tanks," Lt. Col. Damien Pickart, a spokesperson for US Air Forces CENTCOM, told CNN.

The coalition's counter-attack killed more than 100 regime forces, Reuters reported, but a Syrian commander said that only seven were killed and 27 were injured.

Reuters reported that regime forces were likely trying to take an oilfield near Khusham, citing a US official.

Syrian state media characterized the event differently, saying the US had bombed "popular local forces fighting" ISIS, and that it was a US "attempt to support terrorism."