UNITED NATIONS, Jan. 31 -- UN Secretary-General Ban Ki-moon on Saturday condemned the "barbaric murder" of Kenji Goto, after a new video posted online showing the beheading of a man suspected to be the Japanese hostage taken by the Islamic State (IS).

"Once again, the Secretary-General calls for the unconditional release of all hostages held by Daesh and others," said a note released by Ban's spokesperson.

In a one-minute video clip purportedly posted by the militant group IS, a man believed to be Goto appears kneeling on the ground, wearing orange jumpsuit. A man clad in black, wielding a knife and wearing a mask, is stood to the rear of the hostage.

Both Japanese and U.S. officials were trying to confirm the authenticity of the video, though sources close to the matter have suggested the video is authentic based on previous videos.