Authorities have verified the authenticity of a video from the Islamic State group announcing the death of a Japanese hostage, media reports said. Japanese Prime Minister Shinzo Abe said on television the video was likely real, the Associated Press reported, and he'd work to save remaining hostage Kenji Goto.

"To our regret, we have no choice but to say the credibility is high," Abe said, according to the Japan Times. He continued, "Such an act of terrorism is outrageous and impermissible." CBS reported late Saturday Brian Hale, a spokesman for the Office of the Director of National Intelligence, said the U.S. intelligence community has no reason to believe the video is a fake.

Goto appeared in the video, which allegedly came from the extremist group also called ISIS, showing the camera a photo of Haruna Yukawa's body and demanding the release of a prisoner in Jordan.

Doubts about the video's veracity began to emerge Saturday after its release. Users on an ISIS-affiliated website said it was fake and only meant for Goto's family. Others noted the video did not feature a logo for ISIS media group al-Furqan, the AP reported. Goto's wife, Junko Ishido, said his English fluency sounded off.

Abe did not comment on whether he would give in to the demands for the release of Sajida al-Rishawi, a suspected suicide bomber in Jordanian custody since 2005. Japan did not pay up when ISIS previously asked for a $200 million ransom in exchange for the two hostages. Abe said he would not give in to terrorism.

"We will make further efforts to seek the release [of Goto],” Abe said on TV. "We won’t change this stance of ours."

He said Japan would keep supplying people who have fled areas dominated by ISIS with food and medicine. They "keenly need" it, he said, and the video doesn't change that.

Abe said Japan would pursue Goto's release but would not give specifics on how he planned to save the journalist. "We’d like to refrain from discussing how we will deal with [it] because the situation is changing right now,” the Japan Times quoted Abe as saying. “At any rate, we will put our top priority on [saving Goto’s life] and closely cooperate with Jordan to cope with the situation."