U.S. Navy helicopters take off from the Persian Gulf as part of operations targeting Islamic State militants in Iraq and Syria. (Brian Stephens/AP)

The Pentagon on Friday reported the first death of a U.S. military serviceman in Iraq in its new mission to combat Islamic State militants who have seized large areas of Iraq and Syria.

Marine Lance Cpl. Sean Neal, a 19-year-old from California, died in Baghdad on Thursday in what a Pentagon statement described as a noncombat incident. Further details about how Neal died were not immediately available.

Earlier this month, a Marine was deemed lost at sea after he fell from an aircraft into the Arabian Gulf.

The Pentagon said Neal’s death was the first U.S. casualty in Iraq since the Obama administration began its “Inherent Resolve” mission, which now includes airstrikes against the extremist group in Iraq and Syria and a growing number of U.S. military personnel on the ground in Iraq in August.

The Marine’s death is a milestone for the Obama administration, which withdrew U.S. troops from Iraq in 2011 and has sought to ensure the United States is not drawn into more of the costly, messy ground wars that characterized the decade after the 9/11 attacks.

More than 4,000 U.S. military service members died in Iraq after the U.S.-led invasion in 2003.

President Obama, who campaigned on ending that war in Iraq, has vowed that U.S. forces will not return to combat there. But his administration is slowly expanding its involvement in Iraq and neighboring Syria in an effort to defeat the militant group, which threatens not only the Iraqi government but has promised to strike the West.

Americans have set up joint headquarters in Baghdad and Irbil, the capital of Iraq’s northern Kurdish region, as they advise Iraqi forces and support air strikes on Islamic State targets.