The Islamic State terror group (also known as ISIS or ISIL) recently released what it says was a letter written by murdered American-Israeli journalist Steven Sotloff just days before his execution, and justifies his killing by noting that he was a Jew.

Sotloff was beheaded by ISIS days after the first such execution of another journalist, James Foley, in revenge for a US-led air campaign against the jihadi group in Iraq. As the campaign spread to Syria, two other hostages - British aid workers David Haines and Alan Hennings - were similarly executed.

In the latest issue of ISIS's English-language magazine, Dabiq, the group responds to criticism of its decision to systematically execute journalists and aid workers by citing Sotloff's Jewish heritage and Israeli citizenship.

"The case of Steven Sotloff contains a direct refutation against those who portray western journalism and humanitarian aid as purely innocent, for this man was a Jew and citizen of the Jewish state," the article read.

It went on to note that apart from working for several major US publications such as TIME, Foreign Policy and Christian Science Monitory, Sotloff also did freelance work for two Israeli publications: the Jerusalem Post and the Jerusalem Report.

Sotloff graduated from the Interdisciplinary Center Herzliya after studying there between 2005 and 2008, and eventually made aliyah (emigrated to Israel). But testimony from freed European hostages suggest Sotloff's captors did not have any idea he was Jewish or Israeli - despite the reportedly great lengths he went towards to keep his Judaism in captivity.

That was largely down to a concerted campaign by friends, family and associates to scour the internet for any hint of his Jewish or Israeli identity and have the information removed, in the knowledge that his life would be in even greater danger should ISIS find out.

The article cited reports of the campaign to hide Sotloff's identity, and provided a photocopy of his Israeli identity card.

"The war against Islam for the sake of tāghūt [rebelling against Islam - ed.] is a media war as well as a military and intelligence struggle. It is not surprising then to know that dozens of specialists were employed to hide his Jewish identity from the world prior to his execution. This intelligence operation was done in cooperation with the Jewish state and media," it read.

The article ends with the previously-unseen text of a letter it claims was written by Sotloff days before he was beheaded. In it, Sotloff tells his mother that her appeals to ISIS's leader Abu Bakr al-Baghdadi were received but essentially being ignored as long as US airstrikes persisted. In what was likely a pre-scripted appeal by his captors, designed to emotionally torment his family, Sotloff then appeals to his mother to pressure the US government.

"Mom, you can still save my life, just like the families of my previous cellmates who I’m sure you’ve met ," it says, referring to several European hostages released after their governments negotiated with ISIS.

"Pressure our government to not involve themselves in the affairs of these people. At the rate that Obama’s administration is going, this could very well be the last you hear from me. Please don’t let that be the case. Fight for me. I love you."