Iraqi forces in coordination with U.S.-backed Syrian forces have captured five senior Islamic State group (ISIS) leaders, the U.S.-led coalition said Thursday in a statement.

The arrest was a "significant blow to Daesh," coalition spokesman Army Col. Ryan Dillon said, using the Arabic acronym for the extremist group.

A Pentagon spokesman, Marine Maj. Adrian J.T. Rankine-Galloway, said the U.S. credited Iraqi security forces with the militants' capture "on the Iraq-Syria border."

"These arrests are a significant blow to ISIS as we continue to remove its leadership and fighters from the battlefield," Rankine-Galloway said.

ISIS fighters no longer control significant pockets of territory inside Iraq, but do maintain a grip inside Syria along Iraq's border.

The U.S. -led coalition supported Iraqi ground forces and Syrian fighters known as the Syrian Democratic Forces in the more than three-year war against ISIS.

After Iraqi forces retook the Iraqi city of Mosul from ISIS last summer, Syrian forces on the other side of the border claimed a series of swift victories, but the campaign was stalled recently when Turkey launched a cross-border raid into Syria's north.

Earlier this month the coalition announced a drive to clear the final pockets of ISIS territory inside Syria.

An error occurred while retrieving the Tweet. It might have been deleted.

U.S. President Donald Trump tweeted about the anti-ISIS raid Thursday, saying those arrested were the "five most wanted" ISIS "leaders." It was unclear what criteria, if any, Trump was using to describe the ISIS operatives as the "five most wanted."

A U.S. national security official said there were no indications that the operation had captured Abu Bakr al-Baghdadi, the leader of ISIS who has long been the coalition's top target. The official wasn't authorized to discuss the targets publicly and requested anonymity.

Last year the Pentagon said that there were "some indicators" that al-Baghdadi was still alive a month after Russia claimed to have killed him in a strike near the Syrian city of Raqqa.

None of the statements released Thursday from the president or the coalition named the ISIS fighters arrested.

ISIS fighters swept into Iraq in the summer of 2014, taking control of nearly a third of the country. At the height of the group's power their self-proclaimed caliphate stretched from the edges of Aleppo in Syria to just north of the Iraqi capital Baghdad.

Now, with the group's physical caliphate largely destroyed, anti-ISIS operations are increasingly focused on targeting the extremists' remaining leadership.