Israel said on Thursday it had prevented local media from reporting that slain US journalist Steven Sotloff was also an Israeli citizen, in a bid to reduce the risk to him after he was seized by Islamist insurgents in Syria last year.

Islamic State, a militant group which has overrun large areas of Syria and Iraq, released a video this week of Sotloff being beheaded, calling the execution retaliation for US air strikes. His Israeli dual nationality was made public after the White House authenticated the footage.

Sotloff immigrated in 2005 to Israel, whose government became aware of his second citizenship "at an early stage" of his captivity, Foreign Minister Avigdor Lieberman said.

"The censors issued a gag order against reporting that he was an Israeli citizen. We are also in close touch with the United States on this entire matter, both ISIS (Islamic State) and the journalist Sotloff," he told Israel's Channel 10 TV.

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