The US-led coalition has killed as many as 150 Islamic State fighters in an operation in the middle Euphrates River Valley in Syria, officials said Tuesday.

According to a coalition statement, the air strikes took place Saturday near Al-Shafah, in Deir Ezzor province, on an IS headquarters where the jihadists appeared to have been "massing for movement."

"The precision strikes were a culmination of extensive intelligence preparation to confirm an ISIS headquarters and command and control center in an exclusively ISIS-occupied location in the contested middle Euphrates River Valley," the statement read.

While IS has lost most of the terrain they once controlled in Syria, they still remain entrenched in pockets along the middle Euphrates River Valley.

"There's still have a heavy fight going on," said US Central Command spokesman Lieutenant Colonel Earl Brown.

"We are continuing to go after those guys that are trying to reestablish themselves. It's a hard fight right now."

The coalition said that the Syrian Democratic Forces, a US-backed Arab-Kurdish alliance fighting IS, had assisted in target observation prior to the strike.

"The combination of intelligence and continuous eyes on the target ensured no accidental engagement of non-military personnel," the statement read.

The coalition's highlighting of the SDF's role comes as Kurdish fighters in northern Syria are under assault by Turkey.

Washington is treading a fraught line in Syria, on the one hand trying to maintain its relationship with NATO ally Turkey -- which views Kurdish fighters as terrorists -- while on the other continuing to support Kurdish ground forces that have been critical to the defeat of IS.

"Our SDF partners are still making daily progress and sacrifices, and together we are still finding, targeting and killing ISIS terrorists intent on keeping their extremist hold on the region," Major General James Jarrard said.