A Jordanian government spokesman said two prisoners were executed by hanging early Wednesday, including a would-be female suicide bomber from Al Qaeda, according to news reports.
Government spokesman Mohammed Momani said the prisoners were Sajida Rishawi and Ziad Karbouli.
Rishawi, an Iraqi, had been on death row for her role in a triple hotel bombing in Amman, the Jordanian capital, in 2005 that killed dozens.
The executions came after the gruesome death of a captive Jordanian pilot, burned alive in a cage in a grisly spectacle posted on the Internet, drew global revulsion Tuesday as the Jordanian government braced for possible unrest and vowed prompt retaliation against his Islamic State killers.
Jordanian state television confirmed the death of Lt. Moaz Kasasbeh, 26, saying he had been "martyred" a month ago. If true, that would mean a recent push for his release in a prisoner swap had been in vain.
"The blood of the martyr hero will not go to waste," declared an army statement read on Jordanian state TV. "It will be vengeance equal to the tragedy of all the Jordanians."
The hostage drama had transformed the pilot into a national hero in Jordan, where images of him, often wearing a blue military beret, have become ubiquitous on television, newspapers and posters.
His ghastly killing plunged an irate nation into profound mourning amid concern that mass protests could erupt, either demanding retaliation or questioning the kingdom's involvement in the U.S.-led offensive against Islamic State.
By its actions, analysts said, the militant group appeared determined to persuade supporters and potential recruits that it remains ruthless, undaunted and committed to its radical vision of an Islamic "caliphate," despite a string of recent battlefield reversals in Syria and Iraq.
But many say it is a strategy that could backfire in its wanton brutality.
"While ISIS has managed to manufacture a domestic crisis for Jordan, its barbaric killing of the Jordanian pilot will most likely turn Jordanian public opinion and broader Muslim opinion against ISIS," predicted Fawaz Gerges, a Middle East scholar at the London School of Economics, referring to Islamic State by a common acronym.
"I would argue that this is a catastrophic miscalculation on the part of ISIS," Gerges added in an interview. "I have no doubt in my mind that this will represent a tipping point in the Muslim world."
Many analysts have said the militants' aim was to sow dissension in Jordan, which is both a staunch U.S. ally and home to many militant Islamists deeply opposed to Washington's policies in the region.
The video was released, perhaps deliberately, as King Abdullah II, a steadfast ally on counter-terrorism efforts, was on a state visit to Washington. He later met privately with President Obama at the White House. As the meeting got underway, an advisor to the president said Obama planned to reassure Abdullah of the U.S. commitment to fighting the militant group.
Earlier, Obama condemned the "viciousness and barbarity" of the killing and vowed that the U.S.-led coalition would redouble its efforts to make sure that Islamic State is "degraded and ultimately defeated."
But U.S. officials were vague later when asked whether the president's comments indicated any escalation of the U.S.-led campaign, which has already resulted in more than 2,000 airstrikes against Islamic State positions in Iraq and Syria. Both nations share long borders with Jordan.
There were unconfirmed reports that Jordan would hasten the execution of Rishawi. She was an operative of Al Qaeda in Iraq, a predecessor of Islamic State, which had been demanding her release.
The pilot had been in the extremists' hands since Dec. 24, when his F-16 jet crashed in Syria while on a mission with the U.S.-led coalition.
Many observers had assumed that the pilot, a valuable asset for the hostage-takers, would be used in a bid to swap multiple prisoners and extract other concessions from Jordan, perhaps even as a wedge to push Amman out of the coalition.
Instead, Islamic State opted to stage the slaying of a fellow Muslim as its latest and most shocking propaganda vehicle, this one even more disturbing than the group's now-infamous videos featuring the beheadings of hostages, including two U.S. journalists and an American aid worker.
The pilot is from a prominent tribe in the southern city of Karak that, like Islamic State, is Sunni Muslim. Tribal members, important backers of the Jordanian state, had pressured officials to do everything possible to win the release of the pilot. Some had publicly criticized the kingdom's role in the bombing campaign.
Late Tuesday, Jordanian news reports said that the distraught family pushed away photographers who had gathered outside the tribal meeting hall as the pilot's father, Safi Kasasbeh, dressed in traditional Bedouin garb, made his way out of the building.
The government urged a united response.
In a recorded speech to his nation, King Abdullah, scowling under a traditional red and white headdress as he faced the camera, urged Jordanians to "stand as one rank and show the mettle of the Jordanian people in facing the hardships and tragedies that will only strengthen our power and unity."
Speaking on state TV, government spokesman Momani seemed to be addressing those who criticized Jordan's participation with Washington.
For Jordanians "who doubted the savagery of Islamic State, this is the proof," the spokesman said. "He who thought they represented true Islam, then this is the proof."
Momani predicted that the brutal killing would bring Jordanians together "in the face of this evil."
"Those who doubted the unity of the Jordanians in the face of this evil, we will show them the proof," said the government spokesman. "He who doubted that Jordan's response will be decisive and shaking and strong, the proof will come to them, and they will know that the anger of the Jordanians will shake their ranks."
The militants' slick 23-minute video released Tuesday included a rambling screed against Jordan's participation in the "crusader" coalition.
As has become routine in Islamic State videos, the recording showed the doomed man issuing a statement under duress that blamed his government for his death.
The pilot said Jordan had "a traitor Zionist" government, and questioned why it didn't send its forces against "the Jews, who are closer to us." Jordan is one of the few Arab nations that recognize Israel.
He appealed to the families of other pilots to "stop your sons … so that what happened to me does not happen to your sons, and your families are not saddened like mine."
The video builds up to the immolation of Kasasbeh, who is seen in a cage in the midst of a shattered, bombed-out landscape. His left eye is blackened. His orange jumpsuit appears to be wet, probably doused with gasoline or another accelerant.
Nearby, militants in identical fatigues and beige balaclavas, all holding AK-47 rifles, stare ominously from the remains of a smashed building.
A single militant holds a torch, which is lighted by a comrade and then placed on a line of fuel that leads to the cage. The strip of fire quickly races forward and engulfs the makeshift death house. The prisoner flails about helplessly as the flames consume him.
Until Tuesday, there had been some hope that a deal could be reached to free the pilot. The Jordanian government was reported to have been negotiating with Islamic State through intermediaries.
Jordanian authorities had offered a prisoner swap in which Kasasbeh would be freed in exchange for Rishawi.
But in its public comments, Islamic State said only that it would delay the pilot's execution and release a captive Japanese journalist, Kenji Goto, in exchange for Rishawi.
The fates of the Japanese journalist and Jordanian pilot soon became entwined in a wrenching drama that resonated deeply in their homelands, both U.S. allies on opposite sides of the planet.
Jordan said it would not proceed with any deal unless it received proof that the pilot was alive. That proof never came. It was unclear when the government learned that he had been killed on Jan. 3.
On Saturday, Goto was reportedly beheaded by Islamic State. His killing came a week after the reported beheading of another Japanese hostage, Haruna Yukawa.
Bulos is a special correspondent. Times staff writer Christi Parsons in Washington contributed to this report.