AMMAN - The UN Security Council demanded the immediate release of all hostages held by the Islamic State group, as Jordan vowed to do everything it can to save the life of a pilot captured by the militants.
The 15-member council condemned on Sunday the "heinous and cowardly" murder of a Japanese journalist after the jihadist group claimed he had been beheaded.
"Those responsible for the killing of Kenji Goto shall be held accountable," the Security Council said, demanding "the immediate, safe and unconditional release of all those who are kept hostage" by IS and other Al-Qaeda affiliates.
The government of Jordan, meanwhile, vowed to do it all it can to save air force pilot Maaz al-Kassasbeh, who was captured by IS after his plane crashed in Syria in December.
IS militants have seized swathes of territory in Iraq and Syria, ruling with a brutal version of Islamic law. The group has murdered both locals and foreigners, including two US journalists, an American aid worker and two British aid workers.
IS claimed in a video released online Saturday that it had killed 47-year-old Goto - the second purported beheading of a Japanese hostage in a week - but made no mention of the Jordanian pilot it had also threatened to kill.
Jordan's King Abdullah II denounced Goto's murder as a "cowardly, criminal act" and said every effort was being made "to seek the release of the hero pilot Maaz Kassasbeh".
IS has been demanding the release of an Iraqi jihadist on death row in Jordan in exchange for Kassasbeh's life, and Amman said it would hand her over if given proof he is still alive.
The pilot's father Safi Kassasbeh has begged Amman to save his son's life "at any price".
In Japan, Prime Minster Shinzo Abe condemned the "heinous and despicable terrorist acts" of IS and vowed that his country would "never yield to terrorism".
"We will never forgive terrorists," Abe told reporters in Tokyo, appearing to fight back tears as he spoke.
"We will cooperate with the international community to make them atone for their crimes." The video, released Saturday, shows Goto, a respected war correspondent, wearing an orange outfit similar to those worn by Guantanamo Bay inmates, kneeling next to a standing man dressed head-to-toe in black with his face covered.
The man, who speaks with a British accent, appears to be the same IS militant who has featured in previous videos showing the execution of Western hostages.
He addresses Abe, saying the killing was the result of Tokyo's "reckless" decisions - a possible reference to aid it has granted for refugees fleeing IS-controlled areas in Syria and Iraq - and would mark the beginning of a "nightmare for Japan".
The brief video, whose authenticity Tokyo said was "highly probable", ends with the image of a body and a decapitated head on top of it.
'Chills down my spine'
In a statement, Goto's wife Rinko said she was "devastated" by the news.
"While feeling a great personal loss, I remain extremely proud of my husband who reported the plight of people in conflict areas like Iraq, Somalia and Syria," she said.
"It was his passion to highlight the effects on ordinary people, especially through the eyes of children, and to inform the rest of us of the tragedies of war." The couple had a second child just weeks before Goto left for Syria late last year in a bid to find his friend Haruna Yukawa, whom IS claimed it beheaded last week. He was then captured himself.
"I can't find the words to describe how I feel about my son's very sad death," Goto's sobbing mother Junko Ishido told reporters.
Officially pacifist, Japan has long avoided getting embroiled in Middle East conflicts and is rarely the target of religious extremism, so the hostage crisis has been especially shocking for the country.
Many braved Tokyo's chilly streets to pick up the Yomiuri newspaper's special supplement about the Goto video on Sunday.
"It's scary - they (the militants) are saying they'll target Japanese people now," said 21-year-old university student Kyosuke Kamogawa. "That sends chills down my spine." World leaders reacted with outrage to the video, with US President Barack Obama leading international condemnation of the "barbaric" murder.
On Sunday IS added to its long list of atrocities by claiming to have beheaded an Iraqi police officer and a soldier, according to pictures posted online.
IS had vowed to kill Goto and the pilot by sunset on Thursday unless Amman handed over Sajida al-Rishawi, who is on death row for her part in bombings in the Jordanian capital that killed 60 people in 2005.
Last week IS claimed it had beheaded self-described Japanese contractor Yukawa after Tokyo failed to pay a US$200 million (S$270 million) ransom - the same amount it had promised in non-military aid to the region.