TOKYO 

Japan says it is attempting to verify a video released late Saturday that suggests that the Islamic State of Iraq and the Levant (ISIL) has beheaded one of two Japanese hostages, but all signs point to the images being genuine.

A high-ranking government official told the Japan Times Sunday (Saturday GMT) that Tokyo has not confirmed its authenticity, yet United States President Barack Obama offered his commiserations during a flight to India.

“Our condolences today are with the people of Japan for their terrible loss,” Obama said in a statement. “We renew our call for the immediate release of Kenji Goto and all other remaining hostages.”

Secretary of State John Kerry further condemned the "despicable murder," saying in a statement, "America has known this pain and horror ourselves, and we stand with Japan not just in sadness, but in solidarity and strength."

Chief Cabinet Secretary Yoshihide Suga earlier described the suspected act as "outrageous and unforgivable."

"We strongly condemn this,” he told a hastily arranged news conference shortly after midnight in Tokyo. “We demand that [ISIL] not harm Kenji Goto and immediately release him."

The Times reported that the video showed what looked like a still image of journalist Goto holding a picture of what appeared to be the body of fellow captive Haruna Yukawa.

The video was accompanied by a male voice who identified himself as the journalist.

“I am Kenji Goto Jogo," it said. "You have seen the photo of my cellmate Haruna slaughtered in the land of the Islamic caliphate... You were warned. You were given a deadline and so my captors acted upon their words."

"Abe," he says, referring to Japanese Prime Minister Shinzo Abe. "You killed Haruna. You did not take the threat of my captors seriously. And you did not act within that 72 hours."

On Tuesday, Japan's government confirmed the existence of an initial video in which the group threatened to kill the two men within 72 hours unless a ransom of $200 million was paid.

That deadline passed at 2:50 p.m. Friday.

The voice continues by saying that his alleged captors’ latest demand is now easier.

"They are being fair," he adds. "They no longer want money. So you do not need to worry about funding terrorists. They are just demanding the release of their imprisoned sister, Sagda Mubarak Atrous al-Rishawi."

Rishawi, who hails from Iraq, was sentenced to death in Jordan in 2005 following a spate of bombings that targeted three hotels in Amman that left dozens dead or injured, including foreign nationals.

In December last year, Jordanian jihadist leader Mohamed al-Shalabi -- better known as Abu Sayyaf -- urged ISIL to trade a recently-captured Jordanian pilot for her and another prisoner.

“It is simple. You give them Sagda and I will be released,” Kenji says.

The video appeared online at 11 p.m. (1400GMT) but was quickly taken down. 

Japan's Kyodo news agency reported that the same video had also been emailed to the wife of one of the hostages.

SITE Intelligence -- which tracks jihadist propaganda -- reported that the video was posted on ISIL-linked Twitter accounts, but militants on a website affiliated with the group disagreed about its authenticity.

Early Sunday, Abe called for the immediate release of the Japanese journalist, vowing that Japan “will not give in to terrorism” and will continue to make the utmost efforts to save his life.

“[We] can keenly understand how the family [of Yukawa] is feeling. We are speechless,” the Times reported him telling his ministers during an emergency cabinet meeting.

“We firmly denounce” the apparent killing, he added.

“Our country will not give in to terrorism, as we have not [in the past]. We will cooperate with countries across the world and actively contribute to international society’s efforts to cope with terrorism.”

Reports have said that journalist Goto, 47, had travelled to Syria to find and ask for the release of Yukawa, a security contractor reportedly captured in August, when he was taken by ISIL.

ISIL has captured large swathes of land in Iraq and Syria, later declaring the territories under its control an Islamic caliphate.

Three U.S. hostages -- James Foley, Peter "Abdul-Rahman" Kassig and Steven Sotloff -- have been beheaded in ISIL videos since Aug. 19, as well as British citizens David Haines and Alan Henning.

The group also holds British journalist John Cantlie and a 26-year-old American female aid worker, among others.