Beheaded US journalist Steven Sotloff fearless in his coverage of human side to Syria's conflict

Even for a freelance journalist covering the tumult in the Arab world, Steven Sotloff's travels seemed non-stop.

In October 2012, the American reporter was in Benghazi, Libya, covering the aftermath of the deadly raid on the US diplomatic compound. In December, he was in northern Syria, writing about the lives of destitute, displaced Syrians and the war.

"I've been here over a week and no one wants freelance because of the kidnappings. It's pretty bad here," he told a fellow journalist. "I've been sleeping at a front, hiding from tanks the past few nights, drinking rain water."

In August 2013, telling colleagues he understood the dangers, Sotloff returned to Syria, slipping across the border from Turkey. He was soon kidnapped and fell into the hands of Islamic State, the militant group that wants to establish a jihadist hub in the heart of the Arab world.

Islamic State said in a video released on Tuesday that it had beheaded Sotloff, 31, in retaliation for US air strikes, the second such killing of a US journalist in two weeks after the execution of James Foley. President Barack Obama said his country would not be "intimidated".

British Foreign Secretary Philip Hammond said that the masked, British-accented jihadi appeared to be the same person shown in the Foley footage. In the new video, the organisation also threatens to kill another hostage, this one identified as a British citizen, David Cawthorne Haines.