BAGHDAD — One member of a U.S. special operations force was killed during an overnight mission to rescue hostages held by ISIS militants in northern Iraq, the first American to die in ground combat with the militant group, U.S. officials said on Thursday.

Sixty-nine hostages were rescued in the action, which targeted an ISIS prison around 7 kilometers north of the town of Hawija, according to the security council of the Kurdistan region, whose counterterrorism forces took part.

Pentagon press secretary Peter Cook said at a news briefing the operation did not mark a change in U.S. tactics in the war.

“I would not suggest that this is something that is now going to happen on a regular basis, but I do think it is symbolic of the kinds of efforts that we are taking on behalf of our partners,” he told reporters.

It was the most significant raid against ISIS since May, when American special operations forces killed one of its senior leaders, Abu Sayyaf from Tunisia, in a raid in Syria.

The U.S. rescue mission unfolded amid mounting concerns in Washington over increasing Russian intervention in the Middle East.

The hostages rescued in the raid were all Arabs, including local residents and ISIS fighters held as suspected spies, a U.S. official said on Thursday.

More than 20 ISIS militants were killed and six detained, the security council said.

ISIS called the operation “unsuccessful” but acknowledged casualties among its fighters.