Japanese Prime Minister Shinzo Abe said the "credibility" of a video announcing the execution-style killing of a Japanese hostage by the Islamic State militant group was "high."
Speaking on the Japanese TV network NHK on January 25, Abe said he was "speechless" after an online video claimed hostage Haruna Yukawa had been killed.
On the video another Japanese hostage, Kenji Goto, held a photograph of a dead body that was purportedly that of Yukawa.
Abe said, "Such an act of terrorism is outrageous and impermissible, it causes me nothing but strong indignation."
IS threatened on January 20 to kill Yukawa and Goto unless Japan paid a $200-million ransom within 72 hours.
In the video, IS changed its ransom demand for Goto, demanding the release of Al-Qaeda-linked attempted female suicide bomber Sajida Rishwai, an Iraqi held in Jordan, instead of money.
U.S. President Barack Obama released a statement condemning Yukawa's apparent killing.
British Prime Minister David Cameron said in a statement Yukawa's death was "yet another reminder of the murderous barbarity of these terrorists."