ISLAMIC State (Isis) militants have released a video which appeared to show the murder of a journalist at the centre of hostage negotiations with the Japanese government.
In the video Kenji Goto, 47, was shown kneeling in front of a masked man armed with a knife. The film was titled: A Message To The Japanese Government.
Japan and the US said they were checking the authenticity of the film but Japan's chief cabinet secretary Yoshihide Suga said: "I cannot help feeling strong indignation that an inhuman and despicable act of terrorism like this has been committed again. We resolutely condemn this."
Unlike past murders, however, the reported killing followed negotiations with Isis aimed at freeing Mr Goto, and the release of Jordanian pilot Muadh al-Kasasbeh.
Mr Goto, an experienced freelance reporter who went to Syria in October, had previously been forced to hold up a picture which appeared to show the aftermath of the beheading of another Japanese hostage, private security consultant Haruna Yukawa.
The group had initially asked for a $200 million ransom for the release of the two Japanese men.
After Isis reported that Mr Yukawa had been killed, however, the demands changed with a call for Jordan to release Sajida al-Rishawi, who has been held since 2005 in relation to bomb attacks on hotels in Amman.
Jordan has itself been threatened with the murder of Mr Kasasbeh, captured when his plane crashed in Syria on Christmas Eve. In response, it has demanded proof he is still alive.
Isis demanded Rishawi was brought to the Turkish border by last Thursday evening or Mr Kasasbeh would be killed. But no exchange occurred and late on Friday, Japan's deputy foreign minister Yasuhide Nakayama warned negotiations were "in a state of deadlock".
After Isis's ransom demands, his family publicly called for Japan's Prime Minister Shinzo Abe to negotiate.
In the most recent video, the Isis figure spoke with a British-sounding accent. Mr Goto did not speak in the one-minute long film.
Speaking to the camera, the masked man says: "To the Japanese government: You, like your foolish allies in the Satanic coalition, have yet to understand that we, by Allah's grace, are an Islamic Caliphate with authority and power, an entire army thirsty for your blood.
"(Prime Minister of Japan Shinzo) Abe, because of your reckless decision to take part in an unwinnable war, this knife will not only slaughter Kenji, but will also carry on and cause carnage wherever your people are found. So let the nightmare for Japan begin."
Three Americans and two Britons have been killed in similar circumstances, although without public demands for ransoms of money or prisoner exchanges.
US journalists James Foley and Steven Sotloff were beheaded, before British aid workers David Haines and Alan Henning.
Abdul-Rahman Kassig, formerly known as Peter Kassig, an American aid worker, was also killed.
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