An online video released on Saturday night showed an Islamic State militant behead Japanese journalist which ended days of negotiations by diplomats to save the man. "Through his reporting, Goto courageously sought to convey the plight of the Syrian people to the outside world. Our thoughts are with Mr Goto's family and loved ones and we stand in solidarity with Prime Minister Abe and the Japanese people in denouncing this barbaric act," he said.
"We applaud Japan's steadfast commitment to advancing peace and prosperity in the Middle East and globally including its generous assistance for innocent people affected by the conflicts in the region," he added.
"Standing together with a broad coalition of allies and partners, the United States will continue taking decisive action to degrade and ultimately destroy ISIL," Obama said.
In a separate statement, the US Secretary of State John Kerry condemned ISIL's vicious murder of the Japanese hostage. "We extend our sincere and heartfelt condolences to his wife, his family, and his loved ones, as well as to the people of Japan," he said.
"The barbaric killing of Kenji Goto and of Haruna Yukawa before him, shows again ISIL's brutality and extremist agenda. The United States knows this pain on a personal level born of our own experience," he added.
"We share the sorrow and continue to stand shoulder to shoulder with our ally Japan in confronting terrorism. We commend Japan's support for those in the region who have been displaced by ISIL, the Syrian regime, and other militant groups," Kerry said.
"Japan's generous assistance to vulnerable communities fully reflects its commitment to international peace and development," he added. Meanwhile in another statement, the National Security Council Spokesperson Bernadette Meehan said: The United States strongly condemns ISIL's actions and we call for the immediate release of all remaining hostages. We stand in solidarity with our ally Japan".
"We have seen the video purporting to show that Japanese citizen Kenji Goto has been murdered by the terrorist group ISIL. We are working to confirm its authenticity," she said.
The IS had said they will kill Goto and a Jordanian pilot Maaz al-Kassasbeh by sunset Thursday if Amman failed to hand over an Iraqi female jihadist.
US Defense Secretary Chuck Hagel in a statement said the American military will continue to stand alongside its Japanese allies.
"I extend my deepest condolences on behalf of the men and women of the Department of Defense to the family of Kenji Goto. Like many of his journalist colleagues, Mr Goto went to dangerous places to tell stories that needed to be", the statement said.
"His murder, which follows that of his countryman Haruna Yukawa, reminds the world of the threat we confront in the Islamic State of Iraq and the Levant (ISIL), while it
reinforces our global coalition’s commitment to degrade and ultimately destroy ISIL," Hagel said.
"The United States and its military will continue to stand alongside our Japanese allies, and we send our thoughts and prayers to Mr Goto's loved ones and all the people of Japan," he added.
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