The Jordanian air force carried out air strikes against Islamic State targets in Mosul, killing 55 including a top IS commander known as the "Prince of Nineveh," Iraqi media reported Wednesday.
The strikes came just hours after Jordan's King Abdullah II vowed a "severe" response to IS after it burned alive a Jordanian fighter pilot captured in Syria.
"The blood of martyr Maaz al-Kassasbeh will not be in vain and the response of Jordan and its army after what happened to our dear son will be severe," the king said in a statement released by the royal court.
Abdullah held talks with senior military and security officials Wednesday after cutting short a trip to Washington following IS's release of a video showing Kassasbeh's killing.
Information Minister Mohammad al-Momani told AFP Amman was "more determined than ever to fight the terrorist group Daesh," using an Arabic acronym for IS, after the brutal murder of its airman.
According to Reuters, a government spokesman said that Jordan will step up its role in the US-led coalition against IS militants, with all military options on the table.
US President Barack Obama, who hosted Abdullah in a hastily organized and brief Oval Office meeting Tuesday night, led widespread international condemnation of the latest graphic murder, decrying the "cowardice and depravity" of IS.
During the meeting Obama offered "his deepest condolences" to the king. White House spokesman, Alistair Baskey, said that "The president and King Abdullah reaffirmed that the vile murder of this brave Jordanian will only serve to steel the international community's resolve to destroy IS."
Israeli Prime Minister Benjamin Netanyahu offered his condolences to Abdullah as well, saying that radical Islam's "cruelty knows no borders, the greatest threat to humanity would be if these extremists get their hands on nuclear weapons," referring to Iran's nuclear program.
Israeli Foreign Minister Avigdor Lieberman also sent his condolences to Jordan for the pilot's "barbaric" murder.
Lieberman also applauded King Abdullah for "for his powerful actions against the heinous terror," and called on world leaders to follow Jordan's example with fighting terror "because it is impossible to beat terror with words and declarations."
Jordan executes two in response to pilot's slaying
Earlier in the day, Jordan executed two jihadist prisoners by hanging in response to the killing of Kassasbeh, government spokesman Mohammed al-Momani said.
The executions came just hours after IS militants released a video which showed al-Kassasbeh being burned alive in a cage.
Kassasbeh's father said the two executions were not enough and urged the government to do more to avenge his death. "I want the state to get revenge for my son's blood through more executions of those people who follow this criminal group that shares nothing with Islam," Safi al-Kassasbeh told Reuters.
"Jordanians are demanding that the state and coalition take revenge with even more painful blows to destroy these criminals," he concluded.
The European Union, which had released a statement of solidarity with Jordan over the brutal killing of al-Kassasbeh, condemned the executions.
"While all efforts must be made to counter terrorism and hold the perpetrators accountable, our reaction to the threat posed by IS needs to be consistent with our common values on justice and the rights of prisoners," foreign policy chief Federica Mogherini said Wednesday.
'Maximum pain' for coalition
Even for a group infamous for its brutality, the execution of al-Kassasbeh marked a significant escalation, with the group hoping to sow division and fear among their opponents.
"It is a message for the coalition... your men will end up in videos that are even more horrific and will do lasting damage to public opinion in your countries," said Romain Caillet, an expert on jihadist movements.
No "head of state wants to see a young soldier end up in one of these videos," he said.
"It was a huge opportunity for IS to inflict maximum pain on the international coalition, especially to Muslim countries that took part in it," he said.
"The main purpose of this video is to send a message that retribution against fellow Muslims who assist the United States in its fight against the group will be unimaginable."
Iraq-based security expert Hisham Alhashimi agreed, saying the gruesome execution method was intended to evoke the maxim "an eye for an eye".
Jordanian state media said Tuesday that al-Kassasbeh appeared to have been killed on January 3, suggesting the group never planned to exchange the pilot.
It preferred instead the shock and propaganda value of killing him, said Hassan Hassan, an expert at the Delma Institute, a research center based in Abu Dhabi.
The video, more than 22 minutes long, seeks to justify burning Kassasbeh alive by showing footage of the air strikes launched by the US-led coalition in Syria since September.
Sources in Raqqa reported that big screens were set up across the city and played the video throughout the night.
Syria Kurds mourn Jordan pilot as 'martyr' of Kobane
Syrian Kurdish fighters in the battleground town of Kobane commemorated al-Kassasbeh as a "martyr" after his brutal execution by their jihadist foes, an activist said Wednesday.
"After the killing of Maaz was announced, troops from the People's Protection Units (YPG) in Kobane and in liberated villages nearby gathered to mourn the pilot's death, and to hold a minute of silence in his honour," Mustafa Ebdi told AFP.
"He is one of Kobane's martyrs -- everyone is proud of him," Ebdi said, referring to the slain pilot's participation in the US-led air campaign in Syria, which helped Kurdish fighters liberate the town from the Islamic State group last week.
The YPG's political arm, the Democratic Union Party (PYD), vowed to avenge IS's killing of al-Kassasbeh and Japanese fellow captives Kenji Goto and Haruna Yukawa.
The recapture of Kobane "is just the beginning of the defeat of those monsters, so that humanity can be free from them for ever", it said.