Pentagon chief expects more anti-IS raids after captives freed

US Defence Secretary Ashton Carter said Friday that he expected more raids targeting the Islamic State (IS) group similar to the mission in northern Iraq that freed dozens of captives but left an American soldier dead.

Carter's comments came as President Barack Obama tapped veteran Iraq expert Brett McGurk to coordinate the troubled US-led campaign against the IS group, replacing General John Allen, who served in the post for a year.

On Thursday, US forces and Kurdish forces stormed an IS-run prison near Hawijah in northern Iraq, freeing some 70 captives who were facing imminent execution. Five IS militants were captured and several others killed, the Pentagon said.

The Hawijah raid marked an apparent break with the usual role of US forces, who are in Iraq to support government forces but do not directly engage in combat in line with Obama's "no boots on the ground" policy.

But Carter said it was likely not a one-off, noting that a "significant cache" of intelligence had been retrieved.

"I expect we'll do more of this kind of thing," Carter told reporters, referring to the operation.

"One of the reasons for that is that you learn a great deal because you collect the documentation, you collect various electronic equipment and so forth ... So the sum of all this will be some valuable intelligence."

The soldier killed, Master Sergeant Joshua Wheeler of Oklahoma, was the first American serviceman to die in action in Iraq since 2011.

Carter said some of the captives rescued confirmed they had expected to be executed that day, with their graves already dug. 

"Not only did our support help provide another mass killing, we enabled those partners of ours to deliver ISIL a clear defeat," he said, using another acronym for IS.

The operation near Hawijah was part of a broader US-led campaign that began in June of last year targeting the IS group. The disparate 64-member coalition has sometimes struggled, with the White House reluctant to dramatically gear up US involvement and key members of the coalition holding divergent aims and differing degrees of commitment.

The task has only become more complex since Russia and Iran have intervened to prop up the Syrian government and deepen ties with Baghdad.

McGurk had most recently been Allen's deputy, focusing largely on efforts to work with Sunni tribal leaders and the Iraqi government to take back Ramadi.

Praise for US commando

According to unnamed sources cited in other media, Wheeler was part of the elite Delta Force, often used for hostage rescue and other operations.

Wheeler, who had been awarded numerous bronze stars and other commendations, had previously served as an Army Ranger, serving three tours in Afghanistan and Iraq.

He was then deployed 11 times as part of US Special Operations Forces, the Army said.

Carter announced that Wheeler inserted himself into a firefight to defend Kurdish soldiers, even though the plan called for the Kurds to do the fighting, the Associated Press reported. 

"This is someone who saw the team that he was advising and assisting coming under attack, and he rushed to help them and made it possible for them to be effective, and in doing that lost his own life," Carter annouced in a news conference at the Pentagon.

The US defence chief also noted that Wheeler's death "reminds us of the dangers that the coalition forces confront in Iraq, but also of the important assistance they provide local forces as they lead the fight against a barbaric enemy".

Wheeler's body will arrive in the US on Saturday, and Carter said he would be on hand with his own wife and Wheeler's family for the arrival.

The US has 3,500 troops in Iraq to train, advise and assist Iraqi forces in fighting IS.

The US forces did not intend to go inside the compound or be directly involved in the raid, "but the Kurds came under heavy fire," a defence official told AFP, speaking on condition of anonymity.

"They were in need of protection. So the US troops engaged to finish the job."