The Islamic State group's radio confirmed on Sunday that its terrorists have executed Japanese security contractor Haruna Yukawa, following the release of a video announcing the hostage's death, according to AFP. 

"The Islamic State has carried out its threat... it has executed Japanese hostage Haruna Yukawa after the expiry of the deadline given," the Sunni extremist group said on Al-Bayan radio.

"The second hostage (Kenji Goto) is calling on his relatives to put pressure on the (Japanese) government for the release of our sister Sajida al-Rishawi, held in the jails of the oppressors in Jordan, in exchange for his release," it said.

Rishawi is a would-be Iraqi female suicide bomber on death row in Jordan in connection with triple hotel bomb attacks in Amman that killed 60 people on November 9, 2005.

On Saturday, a video uploaded to the terror organization's Twitter account showed the second hostage, Kenji Goto, holding a gruesome photo showing the beheaded body of Yukawa.

The video was released with an audio recording in which a man claiming to be Goto blames Japanese Prime Minister Shinzo Abe for his fellow captive's death because he failed to pay ISIS a $200 million ransom by the end of the 72-hour deadline it announced Tuesday.

The voice also reveals a new demand for the release Rishawi, saying the terrorists are no longer demanding money to save his life, but want "their sister" to be freed."It is simple. You give them Sajida and I will be released," the voice says.

The Amman bombings were claimed by Abu Musab al-Zarqawi, the Al-Qaeda leader in Iraq who was killed in a US air raid there in June 2006.

His group was a precursor of the ISIS group, and Rishawi's brother, Samir Atruss al-Rishawi, who was also killed in Iraq, was one of Zarqawi's lieutenants.

Goto blames Japanese Prime Minister Shinzo Abe for Yukawa's death - and explains that he, too, will be executed unless Jordan releases terrorist Sajedah Rishawi. The $200 million ransom fee claimed in earlier videos has apparently been waived. 

Goto then turns to his wife and tells her of his longing for her and his two daughters, begging Abe "not to kill" him, too. He explains that it is possible to prevent his murder by working with Jordanian officials in his home country. 

World leaders responded with outrage to the clip - compounded by the fact that Yukawa may have been mentally ill - while Japan rushed to confirm the footage's veracity in a race against time. 

Japan's Prime Minister Shinzo Abe stated Sunday morning, however, that the "credibility" of the video is "high" and that the government will continue analyzing the images to fully confirm the authenticity of the video.