WASHINGTON — In a new online threat to American military personnel, the Islamic State has called on its members and sympathizers in the United States to kill 100 service members whose names, photos and purported addresses it posted on a website.

The group said that the personnel had participated in efforts to defeat it in Syria, Iraq, Yemen and elsewhere.

Defense Department and F.B.I. officials said that they were aware of the website and were investigating the posting.

It does not appear that the information had been hacked from government servers. One Defense Department official, who was not authorized to speak publicly, said that most of the information could be found in public records, residential address search sites and social media.