President Barack Obama and Japanese Prime Minister Shinzo Abe Saturday condemned the "heinous murder" of hostage Kenji Goto after the Islamic State group released a video purportedly showing his beheading.
"The United States condemns the heinous murder of Japanese citizen and journalist Kenji Goto by the terrorist group ISIL," Obama said in a statement, using an acronym by which the IS group is known.
"Through his reporting, Mr Goto courageously sought to convey the plight of the Syrian people to the outside world."
The US president also applauded Japan's "steadfast commitment to advancing peace and prosperity" in the Middle East and globally.
The claim was made in a video released online that included no mention of a Jordanian pilot also being held by IS, whom the militant group has also threatened to kill.
A visibly upset Shinzo Abe told reporters in Tokyo: "I am extremely angry about these heinous and despicable terrorist acts. We will never forgive terrorists."
"Japan will never yield to terrorism...(and) is firmly resolved to fullfil its responsibility in the international community's fight against terrorism," he said.
Goto was the second Japanese hostage beheaded by IS, after the group claimed responsibility last week for the killing of self-described contractor Haruna Yukawa, after the expiration of a 72-hour deadline during which the miltants had asked Tokyo to pay a $200 million ransom.
In the video he is seen kneeling next to a standing masked man who speaks with a British accent and blames the Japanese government for his "slaughter."