AMMAN, Jordan (AP) — An online video released Saturday night purported to show an Islamic State group militant beheading Japanese journalist Kenji Goto, ending days of negotiations by diplomats to save the man.

The video, released on militant websites, heightened fears for the life of a Jordanian pilot whose fate had been linked to that of Goto. Earlier this week, Jordan had offered to free an al-Qaida prisoner for the pilot, but a swap never moved forward.

Jordan's government spokesman, Mohammed al-Momani, declined comment late Saturday on the video of Goto's purported beheading.

Japan's Chief Cabinet Secretary Yoshihide Suga said the Cabinet was convening an emergency meeting and was rushing to confirm the authenticity of the online video.

Suga described the online video as a 'deplorable terrorist act."

The video, highlighted by militant sympathizers on social media sites, bore the symbol of the Islamic State group's al-Furqan media arm.

Though the video could not be immediately independently verified by The Associated Press, it conformed to other beheading videos released by the extremists, who now control about a third of both Syria and neighboring Iraq in a self-declared caliphate.

The video, called "A Message to the Government of Japan," featured a militant who looked and sounded like a militant with a British accent who has taken part in other beheading videos by the Islamic State group. Goto, kneeling in an orange prison jumpsuit, said nothing in the roughly one-minute-long video.

"Abe," the militant says in the video, referring to Japanese Prime Minister Shinzo Abe, "because of your reckless decision to take part in an unwinnable war, this man will not only slaughter Kenji, but will also carry on and cause carnage wherever your people are found. So let the nightmare for Japan begin."

U.S. officials said they were trying to confirm the authenticity of the video.

"We have seen the video purporting to show that Japanese citizen Kenji Goto has been murdered by the terrorist group ISIL," said Bernadette Meehan, a spokeswoman for the White House's National Security Council, using an alternate acronym for the extremist group. "The United States strongly condemns ISIL's actions and we call for the immediate release of all the remaining hostages. We stand in solidarity with our ally Japan."

Goto, a 47-year-old freelance journalist, was captured in October, after he traveled to Syria to try to win the release of Haruna Yukawa, a colleague held by the Islamic State group.

Yukawa reportedly was killed previously, though authorities have yet to authenticate the video claiming that.

Saturday's video made no mention of the Jordanian pilot Lt. Muath al-Kaseasbeh, who was captured after his fighter plane went down in December over an Islamic State-controlled area of Syria.

Earlier this week, Jordan had offered to release an al-Qaida prisoner for the pilot. However, in a purported online message earlier this week, the militants threatened to kill the pilot if the prisoner wasn't released by Thursday. That deadline passed, and the families of the pilot and the journalist were left to wait in agony for two days.

Late Friday, Japan's deputy foreign minister reported a deadlock in efforts to free Goto.

The hostage drama began last week after militants threatened to kill Goto and Yukawa in 72 hours unless Japan paid $200 million.

Later, the militants' demand shifted to a release of the al-Qaida prisoner, Sajijda al-Rishawi, 44, who faces death by hanging in Jordan for her role in triple hotel bombings in Amman in 2005. Sixty people were killed in those attacks, the worst terror attack in Jordan's history.

Al-Rishawi has close family ties to the Iraq branch of al-Qaida, a precursor of the Islamic State group.

Jordan and Japan reportedly conducted indirect negotiations with the militants through Iraqi tribal leaders.

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Associated Press writer Jon Gambrell in Cairo contributed to this report.

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Follow Karin Laub on Twitter at www.twitter.com/karin_laub .