The Pentagon has confirmed that it is investigating the Islamic State group's (ISIS) call to "brothers" to kill about 100 U.S. military personnel whose identities were released by the organization.

The Pentagon has not validated the veracity of the call, which was made via an ISIS-linked website.

"I can't confirm the validity of the information, but we are looking into it," an unidentified American defense official was quoted as saying by multiple news outlets.

"We always encourage our personnel to exercise appropriate Opsec [Operational Security] and force protection procedures."

The extremist Islamist organization earlier posted the names, addresses and photos of about 100 U.S. military service personnel, and called on jihadists in the U.S. to kill them.

"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," a post on an ISIS website by the self-proclaimed "Islamic State Hacking Division" said.

A U.S. security source told the BBC that those on the "kill list", who are thought to have participated in the military campaign against ISIS in Iraq and Syria, are being contacted by the authorities.

The details of the list appear to have been taken from public records and do not look like they were stolen from classified U.S. data, an official told the New York Times on condition of anonymity.

This is not the first time ISIS-linked extremists have taken to the Internet to post messages the threaten U.S. interests. U.S. Central Command's Twitter and YouTube accounts were earlier hacked by ISIS-backed militants.