The Pentagon says it killed 150 ISIS fighters in an airstrike in eastern Syria, while the U.S. federal government was shut down Saturday.

The airstrike unfolded in one of the last remaining pockets of ISIS control along the Euphrates River near the border between Syria and Iraq, according to a statement from U.S. Central Command, responsible for American forces in the Middle East.

F-18 fighter jets from the USS Theodore Roosevelt aircraft carrier launched the strike.

While ISIS has lost 98 percent of its territory, the remaining 2 percent held by the terror group includes an area around the Syrian city of Al-Shaafah, where the strike took place. Top U.S. military officials have said they believe the head of ISIS, Abu Bakr al-Baghdadi, is hiding in the area.

U.S.-backed fighters in the Syrian Democratic Forces (SDF) “assisted in target observation prior to the strikes,” according to a statement announcing the airstrike.

The target for the American aircraft was an ISIS headquarters with a “heavy concentration” of ISIS fighters, who were preparing to leave the area, according to the statement. The head of U.S. commandos in Iraq and Syria said the strike shows ISIS has not been defeated.

“The strikes underscore our assertion that the fight to liberate Syria is far from over,” said Maj. Gen. James Jarrard, commanding general of the special operations joint task force.

“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. We cannot take our focus off our mission, and we must not lose our momentum in taking these terrorists off the battlefield and preventing them from resurfacing somewhere else,” Jarrard said.

ISIS continues to “mass large numbers in its attempt to retain a stronghold in Syria,” the statement added.