A newly released video purportedly shows the body of one of two Japanese hostages beheaded by members of the Islamic State group after Tokyo failed to heed a ransom deadline.

The message, posted on jihadist sites on Saturday, consists of a still photo of Japanese national Kenji Goto, with another photo of the allegedly headless body of co-hostage Haruna Yakawa, along with an audio message.

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In the video, Goto allegedly pleads for his life, saying his captors no longer wanted money for his release.

According to him, the radical group will release him in exchange for Sajida al-Rishawa, a jihadist jailed in Jordan for a failed 2005 suicide bombing.

“These could be my last words. Don’t let these be my last words you ever hear,” Goto allegedly says in English.

The authenticity of the video could not be independently verified.

On Tuesday, the radical group threatened in a video posted on the internet to kill Goto, a freelance journalist, and Yakawa, who works for a private security firm, unless a $US200 million ($A248 million) ransom payment was made within 72 hours.

The deadline expired on Friday.