WORLD leaders have reacted with outrage to a new video from the Islamic State showing the beheading of British aid worker David Haines.

British Prime Minister David Cameron released a statement condemning the slaying as “an act of pure evil.”

Cameron confirmed Haines’ death in a statement posted on his official Twitter account after the British Foreign Office had said earlier that it was “working urgently to verify the video.”

Haines is the third Westerner beheaded in recent weeks by the Islamic State group, which has seized vast swaths of territory in Syria and Iraq.

We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes. — David Cameron (@David_Cameron) September 13, 2014

The video released earlier this morning shows both David Haines and his British-accented executioner blaming the British Prime Minister’s support for US air strikes for his death.

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The life of a fourth prisoner, British aid worker Alan Henning, was threatened at the end of the presentation.

“The murder of David Haines is an act of pure evil,” Cameron said, adding that “my heart goes out his family who have shown extraordinary courage and fortitude.”

UK aid worker David Haines beheaded by #ISIS Remember this great & giving man this way not as ISIS wants @ACTED pic.twitter.com/dv9A7uyrRJ — Steve Clemons (@SCClemons) September 13, 2014

“We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes,” Cameron said.

Cameron returned to his residence at 10 Downing Street shortly after midnight and is expected to chair a meeting of the government’s emergency response committee

He vowed “justice, however long it takes”.

US President Barack Obama added his voice to the growing world outrage.

"Those who threaten the United States will find no safe haven." —Obama on our strategy to degrade and destroy ISIL: http://t.co/MyoX3jBJ5Q — The White House (@WhiteHouse) September 13, 2014

“The United States strongly condemns the barbaric murder of UK citizen David Haines by the terrorist group ISIL (Islamic State),” he said.

“Our hearts go out to the family of Mr. Haines and to the people of the United Kingdom. The United States stands shoulder to shoulder tonight with our close friend and ally in grief and resolve. We will work with the United Kingdom and a broad coalition of nations from the region and around the world to bring the perpetrators of this outrageous act to justice, and to degrade and destroy this threat to the people of our countries, the region and the world.”

The murder of David Haines is an act of pure evil. My heart goes out to his family who have shown extraordinary courage and fortitude. — David Cameron (@David_Cameron) September 13, 2014

“We can’t be intimidated by this and we won’t be,” Immigration Minister Scott Morrison told Network Ten this morning in response to the new video.

Since the decision to raise Australia’s terror alert level from medium to high on Friday, it’s been revealed the Defence Security Authority has warned uniformed military personnel they could be targeted by Muslim extremists.

The move was based on one military officer recently being verbally abused in Sydney’s CBD.

EVIL ACT

The video from the Islamic State which shows the death of British aid worker David Haines threatens America’s allies for supporting action in the Middle East.

The video appears intended as a direct threat to British Prime Minister David Cameron:

“For being a lapdog, Cameron, you will drag your people into another bloody and unwinnable war,” the video warns.

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“This British man has to pay the price for your promise, Cameron, to arm the Peshmerga against the Islamic State.”

Islamic State militants have previously beheaded two American journalists and posted video evidence online.

David Haines, 44, is shown in the latest video reciting an Islamic State script. He had been abducted in March 2013 near a refugee camp in Atmeh, Syria, while organising the delivery of humanitarian aid.

“You followed Americans into Iraq, following the trend of British Prime Ministers who cannot find the courage to say no to Americans,” he appears to say

“Unfortunately, it is we the British public, that in the end that will pay the price for our parliaments selfish decisions.”

The executioner, speaking with a British accent, repeats previous threats stating the United States must end its air strikes against jihadists in Iraq.

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“This British man has to pay the price for your promise, Cameron,” he says. “Ironically, he has spent a decade of his life serving under the same Royal Air Force that is responsible for delivering those arms.

“Your evil alliance with America which continues to strike the Muslims of Iraq and most recently bombed the Haditha Dam will only accelerate your destruction.”

The video closes with yet another threat, this time to the life of alleged British captive Alan Henning. He is understood to be an aid worker.

FAMILY MOURNS

The family of David Haines, a British aid worker, have released a statement addressing his execution.

“David was like so very many of us, just another bloke,” his brother, Mike, says.

“David was most alive and enthusiastic in his humanitarian roles. His joy and anticipation for the work he went to do in Syria is for myself and family the most important element of this whole sad affair. He was and is loved by all his family and will be missed terribly.”

Earlier this weekend his parents issued a public plea urging his captors to contact them.

His family said they had not received any reply from the group after repeated messages.

In a short statement released through Britain’s Foreign and Commonwealth Office yesterday and before the video was released showingDavid’ execution, the family said: “We are asking those holding David to make contact with us.”

Haines was abducted in Syria in 2013 while working for an international aid agency.

The British government had managed to keep his kidnapping secret out of concern for his safety until the most recent IS video identified him as a captive.

The Foreign Office said in a statement that the extremists had put Haines’ name in the public domain.

RANSOM CONTROVERSY

The US families of two journalists previously beheaded by Islamic State jihadists were both warned by US government officials they could face prosecution if they raised a ransom for their release.

The executions of James Foley and Steven Sotloff by Islamic State extremists triggered worldwide revulsion and Washington has since declared it is at war with the radicals.

The United States has a policy of never paying ransoms, contending that doing so would endanger Americans all over the world.

Yesterday, a spokesman for Sotloff’s family said the murdered journalist’s parents were told by a White House counterterrorism official last May that they could face prosecution if they paid a ransom in an attempt to secure the release of their son.

“The family felt completely and utterly helpless when they heard this,” Barak Barfi told Yahoo News.

Ppl against beheading argue emotion, not Quran/Sunnah. "omg its gruesome" "omg innocent" We are Muslims not Jews, we argue with daleel. — (س) Abu Aminah (@ghazishami) September 13, 2014

“The Sotloffs felt there was nothing they could do to get Steve out.” He added that Sotloff’s father was “shaking” after the meeting with the official from the National Security Council.

The remarks followed similar comments by Foley’s mother Diane, who told CNN in an interview aired Thursday that her family was warned it could be charged if it tried to come up with ransom money.

The family was also told no prisoners would be exchanged for Foley, nor would the government take military action, she said. It was also told not to go to the media and “trust that it would be taken care of.” The Sotloff’s “heard the same thing the Foleys did,” Yahoo News quoted Barfi as saying.

Secretary of State John Kerry responded to Foley’s remarks Friday, saying he was “really taken aback” and that he was “totally unaware and would not condone anybody” at the State Department making any threatening statements.

James Foley, 40, had covered wars in Afghanistan, Libya and Syria and contributed to GlobalPost, Agence France-Presse and other outlets.

Sotloff, 31, had worked as a freelance journalist for Time, the Christian Science Monitor, Foreign Policy and World Affairs Journal.