The Islamic State in Iraq and Syria (ISIS) on Tuesday threatened to kill two Japanese hostages unless it receives $200 million US 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."

However, Abe and other Japanese officials declined to say whether they'd make the payment to save the men, identified in an extremist video released Tuesday as Kenji Goto Jogo and Haruna Yukawa.

The video, identified as being made by ISIS'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 analyze the tape to verify its authenticity, though Abe offered no hesitation as he pledged to free the men while speaking to journalists in Jerusalem.

"It is unforgivable," said 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 ISIS, which controls a third of Iraq and Syria.

The knife-brandishing militant in the video resembles and sounds like a British militant involved in other filmed beheadings.

'We feel strong indignation'

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. The premier also said the Israeli government, which Japan promised Sunday to co-operate with on counter-terrorism, are sharing information to aid in the hostage crisis. The Israeli prime minister's office declined to comment. 

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," 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 Yukawa, a 42-year-old private military company operator, was kidnapped in Syria after going there to train with militants. 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," 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 Yukawa's company and a former prefectural assemblyman in Ibaraki, north of Tokyo, told Japanese public television station NHK that he had worried "something like this could happen sooner or later."

"I was afraid that they could use Yukawa as a card," Kimoto said.

Goto, 47,  is a respected Japanese freelance journalist who went to Syria to report on the civil war last year, Miki Ebara, NHK World's editor in chief, told CBC News.

Ebara said Goto has been to many conflict zones and disaster areas over a decades-long career.

"He speaks to local people, how they feel about their life, how they suffer, how women suffer in the conflicts," she said. "His reports are always very, very moving for viewers."

Goto went missing shortly after leaving Japan to report on the conflict in Syria in late October. Ebara said while she was shocked to see the video, she was relieved to know Goto was alive.

ISIS has killed hundreds of captives

ISIS 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 is also holding 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. U.S. officials have asked that the woman not be identified out of fears for her safety.

Tuesday's video marks the first time an ISIS message specifically has demanded cash. The extremists requested $132.5 million US from Foley's parents and political concessions from Washington, though neither granted them during months of negotiations before his killing, U.S. authorities say.

ISIS has suffered recent losses in airstrikes by a U.S.-led coalition, and with global oil prices being down, their revenue from selling stolen oil likely has dropped as well. The extremists also have made money from extortion, illicit businesses and other gangland-style criminal activity.

Its militants also recently released some 200 mostly elderly Yazidi hostages in Iraq, fuelling speculation by Iraqi officials that the group didn't have the money to care for them.

Japan relies on the Middle East for most of the crude oil it needs to run the world's third-largest economy. It also has been working to build wider economic ties in the region, like with Abe's current Mideast tour.

With additional reporting from CBC's Kimberly Gale in Tokyo