The Islamic State (IS) group has threatened to kill two Japanese hostages unless they receive $200 million in 72 hours, directly demanding the ransom from Japan's premier during his visit to the Middle East.
Prime Minister Shinzo Abe vowed to save the men, saying: "Their lives are the top priority."
But Mr Abe and other Japanese officials declined to say whether they would make the payment to save the men, identified in an extremist video released today as Kenji Goto Jogo and Haruna Yukawa.
The video, identified as being made by IS's al-Furqan media arm and posted on militant websites associated with the extremist group, mirrored other hostage threats it has made.
Japanese officials said they would analyse the tape to verify its authenticity, though Mr Abe offered no hesitation as he pledged to free the men while speaking to journalists in Jerusalem.
"It is unforgivable," said Mr Abe, now on a six-day visit to the Middle East with more than 100 government officials and presidents of Japanese companies. He added: "Extremism and Islam are completely different things."
In the video, the two men appear in orange jumpsuits like other hostages previously killed by IS, which controls a third of Iraq and Syria.
"To the prime minister of Japan: Although you are more than 8,000 and 500 kilometres from the Islamic State, you willingly have volunteered to take part in this crusade," says the knife-brandishing militant in the video, who resembles and sounds like a British militant involved in other filmed beheadings.
"You have proudly donated $100 million to kill our women and children, to destroy the homes of the Muslims."
Mr Abe said he would send Yasuhide Nakayama, a deputy foreign minister, to Amman, Jordan, to seek the country's support and to resolve the hostage crisis.
Speaking in Tokyo, chief cabinet secretary Yoshihide Suga also declined to say whether Japan would pay the ransom.
"If true, the act of threat in exchange of people's lives is unforgivable and we feel strong indignation," Mr Suga told journalists. "We will make our utmost effort to win their release as soon as possible."
In August, a Japanese citizen believed to be Mr Yukawa, a private military company operator in his early 40s, was kidnapped in Syria after going there to train with militants, according to a post on a blog. Pictures on his Facebook page show him in Iraq and Syria in July. One video on his page showed him holding a Kalashnikov assault rifle with the caption: "Syria war in Aleppo 2014."
"I cannot identify the destination," Mr Yukawa wrote in his last blog post. "But the next one could be the most dangerous." He added: "I hope to film my fighting scenes during an upcoming visit."
Nobuo Kimoto, an adviser to Mr Yukawa's company and a former prefectural assemblyman in Ibaraki, north of Tokyo, told Japanese public television station NKH that he had worried "something like this could happen sooner or later".
"I was afraid that they could use Yukawa as a card," Mr Kimoto said.
Mr Goto is a respected Japanese freelance journalist who went to report on Syria's civil war last year and knew of Mr Yukawa.
"I'm in Syria for reporting," Mr Goto wrote in an email to an Associated Press journalist in October. "I hope I can convey the atmosphere from where I am and share it."
IS has beheaded and shot dead hundreds of captives - mainly Syrian and Iraqi soldiers - during its sweep across the two countries, and has celebrated its mass killings in extremely graphic videos.
A British-accented jihadi also has appeared in the beheading videos of slain American hostages James Foley and Steven Sotloff, and with British hostages David Haines and Alan Henning.
The group also holds British photojournalist John Cantlie, who has appeared in other extremist propaganda videos, and a 26-year-old American woman captured last year in Syria while working for aid groups.
US officials have asked that the woman not be identified out of fears for her safety.
Today's video marks the first time IS specifically has demanded cash for hostages. Though the militant in the video links it to the Japanese funding efforts to counter the militant group, it comes amid recent losses for the extremists targeted in airstrikes by a US-led coalition.
Its militants also recently released some 200 mostly elderly Yazidi hostages in Iraq, fuelling speculation by Iraqi officials that the group could not support them.
This is Mr Abe's second Middle East hostage crisis since becoming prime minister.
Two years ago, al Qaida-affiliated militants attacked an Algerian natural gas plant and the ensuing four-day hostage crisis killed 29 insurgents and 37 foreigners, including 10 Japanese who were working for a Yokohama-based engineering company, JCG Corp. Seven Japanese survived.