A website purportedly run by the Islamic State of Iraq and the Levant (ISIL) group has published what it says are the names, addresses and photos of 100 US military service members, and called upon its sympathisers to kill them.
The Pentagon said after the information was posted that it was investigating the matter. "I can't confirm the validity of the information, but we are looking into it," the Reuters news agency reported, citing an unnamed US defence official on Saturday.
"We always encourage our personnel to exercise appropriate OPSEC (operations security) and force protection procedures," the official added.
The website posting by a group referring to itself as the "Islamic State Hacking Division" encourages supporters to "take the final step" in killing, claiming they have made it easy for them with the release. The website's authenticity and its link to ISIL could not be immediately verified.
"With the huge amount of data we have from various different servers and databases, we have decided to leak 100 addresses so that our brothers residing in America can deal with you," the group said in the English-language posting.
The New York Times reported that it did not look like the information had been hacked from US government servers and quoted an unnamed Defence Department official as saying most of the information could be found in public records, residential address search sites and social media.
The newspaper quoted officials as saying the list appeared to have been drawn from personnel mentioned in news articles about air strikes on ISIL fighters. The armed group controls parts of Syria and Iraq and has regularly been targeted in US-led air strikes.
The posting, addressed to disbelievers, Christians and "crusaders" in the US, included what the group said were the names, military service branch, photos and street addresses of the individuals. The posting includes the military rank of some but not all of those named.