Islamic State militants have executed Japanese journalist Kenji Goto, according to a video released by the group Saturday.

The footage, which is similar to previous videos the Islamic State has released in the past, shows the masked militant known as "Jihadi John" beheading Goto. The video is directed to the Japanese government, and the executioner, speaking in British-accented English says, "Let the nightmare for Japan begin."

The White House National Security Council (NSC) quickly responded to the release of the video. "The United States strongly condemns ISIL's actions and we call for the immediate release of all remaining hostages," NSC spokeswoman Bernadette Meehan said in a statement. "We stand in solidarity with our ally Japan."

The killing of Goto comes less than a week after the militant group beheaded Haruna Yukawa, another kidnapped Japanese national.

Reports of Goto's death were met with an outpouring of sympathy and grief on social media.

Kenji Goto went into ISIS-held territory to rescue his friend, and they beheaded him instead. Rest in peace. — DavidKenner (@DavidKenner)January 31, 2015

Kenji Goto's reporting was a voice of humanity in times of atrocity — Malachy Browne (@malachybrowne)January 31, 2015

In an emotional statement delivered Saturday after the release of the video, Japanese Prime Minister Shinzo Abe said his country would not give in to terrorism. Abe called the deaths of Goto and Yukawa "outrageous," and pledged that Japan would "continue to work with the international community" to combat terrorism.

The Japanese government had said they were working to secure Goto's release, but Japan's deputy foreign minister Yasuhide Nakayama announced Friday that negotiations were "in a state of deadlock" after the latest deadline passed for a prisoner swap.

"Within this extremely severe context, I instructed [officials] yet again that we work together, as one, to [secure the] immediate release of Mr. Goto," Abe said.

Several days after Yukawa was killed, the Islamic State released another video demanding Jordan release its longtime prisoner Sajida al-Rishawi, who was convicted of participating a suicide bombing plot, or else they would soon kill Goto. Jordan has refused to release al-Rishawi until they receive proof that Jordanian pilot Muath al-Kaseasbeh, who is being held by the Islamic State along with Goto, is still alive. The militants have yet to provide such proof.

The 47-year-old Goto, a longtime freelance journalist who covered the war in Syria, entered IS-controlled territory sometime in October, reportedly to look for his friend Yukawa, a security consultant captured by the militants last August. On January 20, they both appeared as prisoners in a video published by the Islamic State. The militants demanded they be paid $200 million dollars or else they would execute the two men.