The U.S. military says American and Afghan military personnel have been fired on while conducting an operation in Afghanistan's eastern Nangarhar province, and one official says there are U.S. casualties.
The official says several U.S. personnel were either injured or killed, but the exact number and other details are not available.
The official spoke on condition of anonymity. A U.S. military spokesman in Afghanistan says in a statement only that both Afghan and U.S. personnel were "engaged by direct firing."
The Taliban and the Islamic State group affiliate both operate in eastern Nangarhar.
The incident comes as Washington seeks to find an end to the war in Afghanistan.