Working with Jordan and other countries, Japan continued to make efforts on Monday to secure the release of a hostage held by the Islamic State group, according to reports. On Saturday, ISIS released a video purporting to announce the execution of one hostage, Haruna Yukawa, while the fate of journalist Kenji Goto remained unclear.

The new video showed Goto showing a picture of Yukawa’s body, while a voice claiming to be of the freelance journalist said that ISIS is seeking the release of Sajida al-Rishawi, a female suicide bomber who attacked a hotel in Jordan in 2005, and who is currently in Jordanian custody, instead of the $200 million originally demanded by the group. In a video released last Tuesday, the Sunni militant group had demanded the ransom be paid within 72 hours for the release of Yukawa and Goto. The deadline to pay the ransom passed Friday.

"We all have one unchanged goal and we will absolutely not give up until the end. And with that faith, we will try our utmost to reach that goal. That's how it is," Yasuhide Nakayama, a Japanese deputy foreign minister sent to Amman, Jordan, to deal with the hostage crisis, said according to The Associated Press.

Yoshihide Suga, a government spokesperson, reportedly said that authorities were analyzing the latest video released by the group, adding that “the likelihood is high” that the video is authentic. A spokesman for the White House National Security Council reportedly said that U.S. intelligence officials were also working to confirm whether the latest video, which is different from the previous ones released by ISIS, was authentic.

Meanwhile, ISIS claimed on Sunday that it had executed Yukawa, 42, who was captured in Syria last August.

"The Islamic State has carried out its threat... it has executed Japanese hostage Haruna Yukawa after the expiry of the deadline given," the jihadist group said on its Al-Bayan radio, according to Agence France-Presse. "The second hostage 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."

Japanese Prime Minister Shinzo Abe said on Sunday that he was "speechless" after the release of the video. "We will never give in to terrorism, and we will actively contribute to the peace and stability of the world together with the international community. We are not wavering at all on this policy," he reportedly said.