An improvised explosive device has killed four American service members in southern Afghanistan, the U.S. military said.

U.S. military spokesman Lt. Cmdr. Christine Sidenstricker said the four were killed in the south in an explosion Tuesday. No other information was released pending the notification of family members.

Violence has spiked the last three years, and the U.S. has more than 60,000 forces in the country, a record number.