The UN Security Council has decried the "heinous and cowardly" beheading of Japanese journalist Kenji Goto by Islamic State militants.
"This crime is, yet again, a tragic reminder of the increasing dangers journalists and others face every day in Syria," the 15-member body said in a statement released on Sunday.
The council said it "strongly condemned" and "deplored" the killing.
IS claimed the 47-year-old journalist's death on Saturday, the second beheading of a Japanese hostage in a week.
In a video clip posted online, Goto is seen kneeling next to a masked man who speaks with a British accent and blames the Japanese government for his "slaughter".
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"Those responsible for the killing of Kenji Goto shall be held accountable," the Security Council stressed, with member states emphasising such acts would only "stiffen their resolve".
The execution came as Jordan scrambled to save captured pilot Maaz al-Kassasbeh, whom IS says it will free in exchange for an Iraqi jihadist on death row in Jordan.
The Security Council demanded "the immediate, safe and unconditional release of all those kept hostage" by IS and other al-Qaeda affiliates, while sending its "deep sympathy and condolences to the family of the victim, to the government of Japan, as well as to the families of all victims of ISIL".
Goto was beheaded after the group claimed the killing of self-described contractor Haruna Yukawa last week, after the expiration of a 72-hour deadline during which the fighters had asked Tokyo to pay a $US200 million ($A258 million) ransom.
