Islamic State has burned alive a Jordanian pilot in a horrific video released by the militant group.
Mu'ath Al Kassasbeh was taken captive by IS when his F-16 fighter jet crashed near Raqqa, Syria, in December.
Images of his murder have been circulated by IS supporters on Twitter.
They show the 26-year-old airman in an orange jumpsuit in a cage with a trail of fuel leading to him.
The fuel is then lit and the cage bursts into flames.
The Minister for Foreign Affairs, Charlie Flanagan, has condemned the murder of the Jordanian pilot.
Charlie Flanagan said the cruel and immoral manner of the killing was "an affront to humanity"
Minister Flanagan expressed deep sympathy to the pilot's family and to the people of Jordan.
The Jordanian government has informed his family he has been killed and vowed an "earth-shattering" response against IS.
"The blood of the martyr will not have been shed in vain and ... vengeance will be proportional to this catastrophe that has struck all Jordanians," said army spokesman General Mamduh al Amiri.
Jordanian state TV said Mr Al Kassasbeh was murdered on 3 January - nearly a month before IS offered to spare his life in return for al Qaeda prisoner Sajida al Rishawi.
Security officials said Al Rishawi, who is on death row in Jordan for her role in a hotel attack that killed 60 people, will be executed in the capital Amman on Wednesday morning, AFP news agency reported.
They said a number of other jihadists will also be executed.
The US said it "strongly condemns" Mr Al Kassasbeh's killing and stands in solidarity with Jordan.
President Barack Obama said he would "redouble the vigilance and determination on the part of the global coalition to make sure" the jihadists are "ultimately defeated."
British Prime Minister David Cameron said the "sickening murder" will only "strengthen resolve" to defeat IS.
The 20-minute video was released on militant websites and bears the logo of IS's al Furqan media service.
Sky News has decided not to show the shocking footage.
Sky's Foreign Editor Sam Kiley said: "I think all of this indicates a level of desperation on behalf of Islamic State."
He added: "This will be a cause of considerable dismay within Jordan."
Emma El Badawy, a Middle East expert from the University of Exeter, told Sky News: "Burning someone alive is absolutely barbaric and it is expressly forbidden in Islam.
"In terms of negotiations, it just proves that ISIS is completely irrational.
"They had a chance to prove to the world that they were rational negotiators - a chance that they hadn't been given before publicly - and they chose to behave in this way.
"I think it just verifies every bit of evidence that these people are thugs and bloodthirsty, barbaric individuals."
Middle East analyst Shashank Joshi said the brutality of the killing would only serve to stiffen resolve in Jordan, and see efforts against the IS extremists stepped up.
He told Sky News: "If their intent was to split the coalition by threatening violence it's almost certainly going to fail.
"I would anticipate Jordan will continue to remain in the military coalition."
In Mr Al Kassasbeh's home town of Ay, which sits in the Karak Mountains 90 miles south of Amman, there have been demonstrations against the country's involvement in the US-led coalition bombing IS.