BAGHDAD, Iraq (CNN) -- A suicide car bombing in the northern Iraqi city of Mosul killed four American soldiers and an interpreter Monday, the U.S. military said.

The military said three soldiers were killed when the bomb exploded near their vehicle. Another soldier died later of wounds.

An interpreter injured in the strike died later as well.

Violence has been dropping in Iraq, but the Mosul area remains one of the more volatile regions because of ethnic tensions and the presence of the al Qaeda in Iraq militant group.

Twenty-two American military personnel have been killed in the war this year, 14 of them in nonhostile circumstances.

The number of troops to die in the nearly 6-year-old war stands at 4,242.