The U.S.-led coalition and its Kurdish Syrian Democratic Forces (SDF) allies repelled an attack by troops loyal to the Russian and Iranian-backed regime of Bashar al-Assad, killing more than 100 of the Syrian government fighters in Deir ez-Zor province.

“We suspect Syrian pro-regime forces were attempting to seize terrain SDF had liberated from Daesh in September 2017,” an unnamed U.S. official told Reuters, using an Arabic name for the Islamic State (ISIS/ISIL).

The forces were “likely seeking to seize oilfields in Khusham that had been a major source of revenue for Daesh [ISIS] from 2014 to 2017,” added the official.

“Neither U.S. officials nor the U.S.-backed coalition have offered details on the identity of attacking forces. The Syrian army is supported by Iranian-backed militias and Russian forces,” notes Reuters.

The U.S. official told the news outlet that the coalition had alerted Russia about the presence of the alliance-backed SDF in the region.

“Coalition officials were in regular communication with Russian counterparts before, during and after the thwarted [enemy] attack,” proclaimed the official.

Reuters reports:

More than 100 fighters aligned with Syrian President Bashar al-Assad were killed overnight when U.S. coalition and coalition-backed local forces repelled their attack in eastern Syria, a U.S. official said on Thursday.

The heavy death toll underscored the large size of the attack, which the U.S. official said included about 500 opposing forces, backed by artillery, tanks, multiple-launch rocket systems and mortars. The official spoke to Reuters on condition of anonymity.

An anonymous U.S. official also told CNN, “We estimate more than 100 Syrian pro-regime forces were killed while engaging (Syrian Democratic Forces) and Coalition forces.”

In a press release, the U.S.-led coalition described the February 7 attack as “unprovoked,” noting that the Assad forces targeted a “well- established Syrian Democratic Forces headquarters” in Syria’s Deir ez-Zor province.

The alliance noted:

In defense of Coalition and partner forces, the Coalition conducted strikes against attacking forces to repel the act of aggression against partners engaged in the Global Coalition’s defeat-Daesh [ISIS] mission.

The Coalition remains committed to focusing on the defeat-Daesh mission in the Middle Euphrates River Valley and asserts its non-negotiable right to act in self-defense.

The U.S. has indicated the American military will not hesitate to defend itself from aggression from troops loyal to the Russian and Iranian-backed Assad regime.

According to the U.S.-led alliance, there were some coalition troops embedded with the Kurdish-Arab SDF alliance when the attack took place.

There were no American casualties, but the Assad troops did wound one SDF fighter, according to Reuters.

The SDF is led and mostly comprised of fighters from the People’s Protection Units (YPG), the armed wing of the Kurdish Democratic Union Party (PYD) that controls vast swaths of Northern Syrian.

Currently, the YPG is also fighting off a Turkey-led invasion in northern Syria’s Afrin region.

Syrian Kurdish officials said they reached out to the Assad regime for assistance, to no avail.

Although Turkey has backed opposition troops since the Syrian conflict began in 2011, Ankara has moved closer to Assad’s ally, Moscow.

America’s support for the YPG has alienated America’s NATO partner, Turkey, which considers the Syrian Kurdish group to be terrorists.

Some Syrian Kurds have accused Russia of backing the Turkey invasion in Afrin.

The Kurds reportedly refused to hand over Afrin to Russia and Assad in exchange for assistance against Turkey.

Syrian state media reportedly described the incident as “new aggression.”