WASHINGTON — A U.S. military member assisting Iraqi forces in their push to retake Mosul was killed by a roadside bomb Thursday, marking the first American combat casualty in the campaign to oust the Islamic State group from its last major stronghold in northern Iraq.

U.S. officials said the American was fatally wounded near the town of Bashiqa, north of Mosul. He was operating as an explosive ordnance disposal specialist in support of Kurdish peshmerga fighters who are part of an effort to recapture Mosul that began Monday.

A senior U.S. defense official said the service member was in an armored vehicle traveling with Iraqi special forces northeast of Mosul when the vehicle hit a roadside bomb, possibly rolling over.

The soldier was taken by medevac to the Kurdish regional capital, Irbil, but died of his wounds. The official was not aware of any others wounded in the blast.

The officials spoke on condition of anonymity because they were not authorized to publicly discuss details. The American’s identity was being withheld pending notification of his family.

He was the fourth U.S. combat death in Iraq since the U.S. began military operations against the Islamic State with airstrikes in August 2014.

Defense Secretary Ash Carter said the death was a “reminder that our people who are participating in the counter-ISIL campaign, whether they be flying aircraft or working with the Iraqi security forces and the other forces and enabling their consistent advances of the kind that we see in the region of Mosul today, are in harm’s way.”

He added “this is necessary work, because it’s necessary for us to destroy ISIL in Iraq and Syria.”

Roadside bombs and other emplacements of improvised explosive devices pose a particular danger to advancing troops.