A video purported to have been released by the Islamic State in Iraq and the Levant (ISIL) claims the armed group killed one of two Japanese hostages after a deadline passed for Japan to pay the group $200 million in ransom for their freedom.
The video, published online Saturday, reportedly shows the killing of Haruna Yukawa, a private military contractor who was kidnapped in Syria last August.
While Japan has not yet verified the authenticity of the video, Japanese Prime Minister Shinzo Abe on Sunday called the killing of a Japanese captive by the militants "outrageous" and demanded the group release a second Japanese national they are holding.
Abe, speaking to public broadcaster NHK, said chances were high that an image of what appeared to be the decapitated body of captive Yukawa, was authentic.
The Japanese leader called for the immediate release of the remaining Japanese captive, veteran war correspondent Kenji Goto, and said saving Goto's life was a top priority.
Still, Abe reiterated that Japan would not give in to "terrorism."
"Such an act of terrorism is outrageous and impermissible, which causes me nothing but strong indignation," Abe said. "Again, I strongly demand that Mr. Kenji Goto not be harmed and be immediately released."
In the video, ISIL allegedly amended its ransom demand to a prisoner exchange. The group reportedly wants to trade Goto for an ISIL member held in Jordanian custody.
On Friday, ISIL posted an online warning that the "countdown has begun" to kill Yukawa and Goto. The posting showed a clock counting down to zero, along with graphic images of other hostages – including American photojournalist James Foley and aid worker Peter Kassig – who were beheaded by the armed group that has taken over large swathes of Syria and Iraq.
Goto's mother on Friday appealed for her son's rescue.
"Time is running out. Please, Japanese government, save my son's life," said Junko Ishido.
"My son is not an enemy of the Islamic State," she said in a tearful appearance in Tokyo.
ISIL is also holding British photojournalist John Cantlie and an American woman captured last year in Syria while working for aid groups. U.S. officials have asked that the woman not be identified out of fears for her safety.
ISIL has suffered recent losses in airstrikes by a U.S.-led coalition, and with global oil prices down, its revenue from selling stolen oil has likely dropped as well. The fighters have also made money from extortion, illicit businesses and other criminal activities.
ISIL fighters recently released some 200 mostly elderly Yazidi hostages in Iraq, fueling speculation by Iraqi officials that the group did not have the money to care for them.
Al Jazeera and wire services