Daesh (IS) group released a video Tuesday purportedly showing a Jordanian pilot being burned alive in a cage, in the most brutal execution yet of a foreign hostage.
The highly choreographed 22-minute video released online showed images of a man purported to be First Lieutenant Maaz al-Kassasbeh, captured in December, engulfed in flames.
King Abdullah II cut short a visit to Washington to fly home, state television said, as Amman confirmed the death of the 26-year-old fighter pilot and vowed an "earth-shattering response".
The video, whose authenticity was not immediately verified, enraged officials and the army in Jordan vowed to avenge the murder of the 26-year-old pilot.
State television said Kassasbeh had already been killed on January 3, before Daesh offered to spare his life and free a Japanese journalist in return for Rishawi's release.
US President Barack Obama denounced the apparent killing as "just one more indication of the viciousness (and) barbarity".
The United States will "redouble the vigilance and determination on the part of the global coalition to make sure" the group is "ultimately defeated", he added.
The White House said US intelligence was working to confirm the video's authenticity.
The chief of the US-led war on Daesh, General Lloyd Austin, condemned the pilot's murder as "savage" and vowed to "fight this barbaric enemy until it is defeated".
British Prime Minister David Cameron said the "sickening murder will only strengthen our resolve to defeat Daesh".
Kassasbeh was captured on December 24 after his F-16 jet crashed during a mission over northern Syria as part of the US-led campaign against the jihadists.
The video released Tuesday shows footage of him at a table recounting coalition operations against Daesh, with flags from the various Western and Arab countries in the alliance projected in the background.
It then shows Kassasbeh dressed in an orange jumpsuit and surrounded by armed and masked IS fighters in camouflage.
It cuts to him standing inside the cage and apparently soaked in petrol before a masked man uses a torch to light a trail of flame that runs to the cage and burns him alive.
The video also offered rewards for the killing of other "crusader" pilots.
The release of the video of Kassasbeh's purported murder came after Daesh beheaded two Japanese hostages within a week.
'Horrific, disgusting' footage
Daesh group had vowed to kill the second Japanese, Kenji Goto, and Kassasbeh by sunset on January 29 unless Amman handed over Rishawi.
Kassasbeh's plane was the first loss of an aircraft since the US-led coalition launched strikes against IS last year.
Along with Jordan, Saudi Arabia, the United Arab Emirates and Bahrain are taking part in the air strikes in Syria.
Australia, Belgium, Britain, Canada, Denmark, France and the Netherlands are participating in Iraq.
Shiraz Maher, from the International Centre for the Study of Radicalisation at King's College London, described the footage as "simply the most horrific, disgusting thing I have seen from Daesh in the last two years".
"They clearly want to make a real point. This is the first individual whom they have captured who has been directly involved with the Western coalition in fighting Daesh. It is different from the aid workers... This is an act of belligerence.