By Catherine Philp and Sara Elizabeth Williams

Islamic State militants plumbed new depths in depravity last night as they released a video showing a captured Jordanian pilot’s agonising death by fire.

In the footage, which was clearly intended to shock the world, Flight Lieutenant Muath al-Kasaesbeh is seen standing in a large cage, wearing an orange prison suit, as a line of oil leading towards him is lit. He is engulfed in flames and falls to his knees in prayer.

Masked fighters then heaped broken bricks and other debris over the cage, which a bulldozer flattened with the pilot’s body still inside.

The Jordanian government said it had confirmed that Flight Lieutenant al-Kasaesbeh had been killed on January 3, ten days after he was captured on Christmas Eve when his fighter jet came down during a bombing raid on the Isis stronghold of Raqqa in Syria. The video’s release appears to have been timed to coincide with King Abdullah’s visit to Washington.

Jordan vowed last night to avenge the murder of Flight Lieutenant Muath al-Kasaesbeh. As King Abdullah flew home, he was expected to issue a decree authorising the expedited execution of several Islamists already on death row.

“The blood of the martyr will not have been shed in vain,” General Mamduh al-Amiri, the army spokesman said. “Vengeance will be proportional to this catastrophe that has struck all Jordanians.”

Security sources said that revenge would include the expedited execution of a failed female suicide bomber who Jordan had offered to exchange for the pilot. One source said she and three other Islamists would be hanged at dawn today.

Burning a hostage to death signals a new tactic for Isis, which has previously beheaded western hostages while releasing for ransom those whose government was prepared to pay.

Even al-Qaeda followers were horrified, with social media linked to the terrorist network’s most potent Yemeni branch noting that Islam prohibits “execution” by fire. The idea of burning Flight Lieutenant al-Kasaesbeh may have come from Twitter, after Isis supporters started a campaign to come up with ideas for his murder.

President Obama described the footage as “just one more indication of the viciousness and barbarity of this organisation”. He said: “It will redouble the vigilance and determination on the part of the global coalition to make sure that they are degraded and ultimately defeated.” David Cameron tweeted: “Flight Lieutenant Muath al-Kasaesbeh’s sickening murder will only strengthen our resolve to defeat Isis.”

Isis threatened last week to kill Lieutenant al-Kasaesbeh unless Jordan released Sajida al-Rishawi, an al-Qaeda prisoner on death row, in exchange for a Japanese hostage, Kenji Goto.

On Saturday, Isis released a video showing Mr Goto’s beheading but gave no word of the pilot’s fate.

Suspicions that Lieutenant al- Kasaesbeh was long dead have been circulating in Jordan and Syria. He had not been seen or heard of in Isis propaganda video or audio since shortly after his capture.

There was no indication in last night’s video of when it was shot but the length of the footage, 20 minutes, and its slick production suggested it was not quickly made.

Isis posted photos of Lieutenant al-Kasaesbeh immediately after his capture being carried from the scene, naked from the waist down, enraging Jordanians.

In a video released soon after, he was asked what he thought would happen to him. “They will kill me,” he replied.

Isis went on to post several videos featuring comments from people living under Isis rule saying that the pilot should be killed.

Many analysts believe that Lieutenant al-Kasaesbeh’s chances of survival or release were almost nil because of the greater propaganda value his killing could have for the jihadist group.

The capture of the officer, the scion of a powerful Jordanian tribe, has rocked Jordan and brought rare dissent against the ruling monarchy out into the open as the country wrestles with divisions over its involvement in the anti-Isis coalition.

Isis have spoken of their desire to expand into Jordan and have sought to exploit the pilot’s captivity to stir up dissent against King Abdullah. Protests have taken place in Amman and in the pilot’s home town, Karak, calling for Jordan to pull out of the anti-Isis coalition.

Addressing the tribal gathering last night, Ali al-Dalaeen, a former MP, said: “The decision to join the coalition was made in the west; they destroyed Iraq before and now they are trying to destroy Syria. I call for a march of a million to withdraw Jordan from the coalition.”

Opposition to Jordan’s role in the US-led war on the jihadists is compounded by pro-Isis sympathies from a growing number of radicals opposed to its autocratic, western-allied government. After Saudi Arabia, Jordan is thought to provide the second largest number of Isis’s foreign volunteers.

The brutality of Isis’s actions, however, may have backfired. Hundreds took to the streets of Amman last night vowing revenge on the jihadist group.

The video of the pilot’s killing began appearing on jihadist websites last night within an hour of a meeting between King Abdullah and John Kerry, the US secretary of state, in Washington. The monarch quickly cut short his trip to return to Jordan.

Mr Kerry expressed solidarity with Jordan as a member of the coalition, and has signed an agreement that will double aid to Amman to help it cope with the fallout from the turmoil in the region.