King Abdullah was greeted by supporters as he returned to Jordan after a trip to the US
Jordan's King Abdullah II has promised to fight back hard against Islamic State, saying that the death of a Jordanian pilot at the militants' hands will not be in vain.
The remarks were made as the king held a crisis meeting with security chiefs.
He cut short a US trip after IS posted a video showing pilot Moaz al-Kasasbeh being burned alive.
Jordan executed two convicts, including failed female suicide bomber Sajida al-Rishawi, in response.
Lt Kasasbeh was seized after crashing during a bombing mission by the US-led coalition over Syria in December.
Jordan had sought to secure Lt Kasasbeh's release in a swap involving Rishawi, but IS is believed to have killed him a month ago.
The BBC's Paul Adams in Amman says talk of an exchange appears to have been an IS tactic to string Jordan along and foster doubt among Jordanians over its role in the US-led coalition.
'Undermine and degrade'
The king was greeted by a crowd of several thousand people at Jordan's main airport on his return from the US, with many holding up pictures of the monarch and the country's flag in a show of support.
After a meeting with security chiefs, AFP news agency quoted him as saying in a statement: "The blood of martyr Moaz al-Kasasbeh will not be in vain and the response of Jordan and its army after what happened to our dear son will be severe."
Meanwhile government spokesman Mohamed al-Momani said a collaborative effort was needed between members of the US-led coalition to "undermine, degrade and eventually finish [Islamic State]".
"This evil can and should be defeated," he said, adding that Jordan was "more determined than ever" to fight the militant group.
Analysis: Frank Gardner, BBC Security Correspondent
In addition to the horrific voyeurism of the latest hostage murder video from IS, something else stands out - the total inability of the US and its coalition allies to save hostages from the clutches of IS.
For all its multi-billion-dollar intelligence-gathering agencies, its satellites in space, and its highly trained special operations teams, Washington has been unable to mount a successful hostage rescue mission in IS territory.
So this video is not just a warning to Arab pilots taking part in the US-led air strikes, it is a calculated mockery of coalition impotence to stop them murdering their hostages, slowly, in broad daylight, at a time of their choosing.
Everyone knows their base is in Raqqa in northern Syria, and it is no secret that other hostages are still in IS hands.
Efforts may now be increased to find them but an earlier US rescue mission failed, and planners will be looking at the long odds against another one having any more success.
The Jordanian military vowed an "earth-shattering" response after IS posted a video online appearing to show the pilot in a cage engulfed in flames.
Failed suicide bomber Sajida al-Rishawi had been on death row in Jordan for nearly a decade
Safi al-Kasasbeh, the pilot's father, called on Jordan's government to do more than execute prisoners
Rishawi and al-Qaeda operative Ziyad Karboli - both Iraqi nationals - were hanged at 04:00 local time (02:00 GMT) on Wednesday, just hours after the video emerged.
Rishawi had been on death row for her role in attacks in Jordan's capital, Amman, which killed 60 people in 2005. Karboli was convicted in 2008 of killing a Jordanian national.
IS militants had sought Rishawi's release as part of a deal to free captive Japanese journalist Kenji Goto, but later killed him.
BBC