In Syria, 37 militants affiliated to the extremist Islamic State group and an al-Qaida-linked group were killed in two strikes, the United States military said Sunday.

Two of the dead were senior militants, it said.

U.S. Central Command said it struck northwestern Syria on Tuesday, targeting a senior militant from the al-Qaida-linked Hurras al-Deen group and eight others. They say he was responsible for overseeing military operations.

They also announced a strike from earlier this month on Sept. 16, where they conducted a "large-scale airstrike" on an IS training camp in a remote undisclosed location in central Syria. That attack killed 28 militants, including "at least four Syrian leaders."

"The airstrike will disrupt ISIS' capability to conduct operations against U.S. interests, as well as our allies and partners," the statement read.

There are some 900 U.S. forces in Syria, along with an undisclosed number of contractors, mostly trying to prevent any comeback by the extremist IS group, which swept through Iraq and Syria in 2014, taking control of large swaths of territory.

U.S. forces advise and assist their key allies in northeastern Syria, the Kurdish-led Syrian Democratic Forces, located not far from strategic areas where Iran-backed militant groups are present, including a key border crossing with Iraq.