King Abdullah of Jordan has pledged to wage “relentless war” on Islamic State and step up his country’s role in the US-led coalition after the brutal murder of a pilot captured during a raid on jihadi targets in Syria.

“We are waging this war to protect our faith, our values and human principles, and our war for their sake will be relentless and will hit them in their own ground,” state TV quoted the king as saying shortly after his return from Washington to handle one of the worst crises of his reign.

Abdullah was meeting military commanders and security chiefs in Amman to discuss the next moves after Tuesday’s internationally condemned news that Muadh al-Kasasbeh had been burned alive while locked in a cage by his captors. Jordanian officials said all options remained open. But it still seemed unlikely, despite the angry and determined mood, that the kingdom would risk ground operations, informed sources said – not least because the main strongholds of Isis are far away in northeastern Syria and across the border in Iraq.

“We are talking about a collaborative effort between coalition members to intensify efforts to stop extremism and terrorism to undermine, degrade and eventually finish Daesh [the Arabic name for Isis],” said Mohammad al-Momani, the chief government spokesman.

Diplomats in Amman predicted that Jordan would now intensify its role in air attacks on Isis and give them a higher public profile. “There will be some sort of announcement to increase air strikes,” said one. “They will want to show they have a military strategy to hit back at the people who have done this to their boy.”

US officials confirmed that Jordan had suspended its air operations after Kasasbeh’s F-16 came down near Raqqa in Syria on 24 December, but insisted it remained committed to the coalition. Officials in Washington also confirmed that the United Arab Emirates, another of the Arab participants, had also halted air strikes because of inadequate plans for the rescue of downed pilots.

Fox News website embeds unedited Isis video showing brutal murder of Jordanian pilot Read more

Meanwhile, it is thought that Jordan will soon execute four more convicted terrorists who are currently on death row after two hangings early on Wednesday. Sajida al-Rishawi, the Iraqi militant, who was sentenced to death for her role in a 2005 suicide bomb attack that killed 60 people, and Ziyad Karboli, an Iraqi al-Qaida operative who had been convicted in 2008 for killing a Jordanian, were executed at dawn on Wednesday.

The speed with which the executions were carried out suggested a contingency plan the authorities had prepared because they had known for some time that Kasasbeh was dead, probably from their own intelligence sources, and had been waiting for an announcement from the jihadis.

Rumours were circulating on social media as early as 8 January that the 26-year-old pilot had been burned alive and that Isis had been celebrating in Raqqa. The significance is that the negotiations to free Kasasbeh, together with or separately from two Japanese nationals who were later decapitated, were in fact meaningless. It is likely also to explain why the Jordanian government asked for “proof of life” before agreeing to release Rishawi.

In the 23-minute propaganda video that ended with his immolation, Kasasbeh, dressed in an orange jumpsuit, revealed that planes from Saudi Arabia, the UAE and Morocco had taken part in the operation that ended in his capture.

It was apparently the first such operation for Morocco, like Jordan a poor, western-backed monarchy, since it quietly signed up to fight Isis in mid-December. Kasasbeh, clearly speaking under duress, also listed Kuwait, Oman and Qatar as members of the coalition, though they are providing the use of airbases and not taking part in combat operations and are trying desperately to keep a low profile. He described coalition weapons systems and aerial surveillance methods.

Another potentially damaging revelation in the film was the names, ranks, photographs and home towns of scores of fellow Jordanian air force pilots, shown along with an offer of 100 gold dinars (roughly $20,000) for each one killed. This section was headed “security database”. Each one was headed “wanted dead”.

Sources in Amman suggested they may have been taken from Kasasbeh’s phone, or obtained by torture. This will clearly require changes to security procedures.

Experts described the video as more sophisticated than anything previously produced by Isis. It included graphic and disturbing images of civilian casualties, often badly burned or mutilated small children, apparently victims of coalition air attacks, and bodies being pulled from bombed ruins. It also included maps and high-resolution satellite pictures of coalition air bases.

UAE halted Isis air attacks after pilot capture Read more

But it was also a crude and menacing message to Jordanians, whose government was described as “treacherous and Zionist”, to stop fighting Isis. King Abdullah, shown meeting Barack Obama, was described as a “tyrant” who “protects the Jews” and their control of Muslim holy places in Jerusalem and helped Bashar al-Assad slaughter innocents in Syria. The cooperation of Jordan’s intelligence services with the west was part of an “endless chain of treachery”.

Support for the war so far has been distinctly lukewarm, with critics questioning why Jordan is fighting alongside the US.

In recent days, criticism had extended to Abdullah’s loyal tribal constituency, and members of Kasasbeh’s tribe have protested against the government.

The diplomats said they believed there would be short-term support and solidarity behind tougher Jordanian action against Isis because of the horrific manner of Kasasbeh’s death. ”Everyone is on side for now and the king was welcomed back very warmly, but that is likely to be for the short term,” one western source said.

“In the longer term, we will see that undercurrent of questioning Jordan’s role in the coalition come back. As grief turns into anger and anger turns into blame, we will see the tone of the debate change. There is clearly a recognition that the government needs to communicate better to maintain support.”