British Prime Minister David Cameron told an emergency security meeting at Whitehall Sunday the U.K. cannot ignore the threat the Islamic State poses. Cameron, who described Islamic State, or ISIS, militants as "monsters," spoke less than a day after the extremists released a video purportedly showing the beheading of David Haines, an aid worker who was kidnapped in Syria, and threatening to kill a second British hostage, Alan Henning.

Cameron condemned ISIS as the "embodiment of evil" and called Haines a "hero," the Guardian reported.

"We are a peaceful people. We do not seek out confrontation, but we need to understand we cannot ignore this threat to our security and that to our allies. There is no option of keeping our heads down that would make us safe. The problem would merely get worse, as it has done over recent months, not just for us but for Europe and the rest of the world," Cameron said speaking before two union jack flags. "We cannot just walk on by if we are to keep this country safe. We have to confront this menace."

Cameron said in  an official statement the government would provide arms to the Iraqi government and Kurdish peshmerga fighters, support U.S. airstrikes and continue humanitarian aid. He left open the option of joining in the airstrikes but appeared to rule out ground troops.

Parliament is currently in recess and Cameron made no mention of calling lawmakers back. He said, however, he would consult with Parliament before taking military action. The Daily Telegraph said he likely would wait until after Thursday's referendum on Scottish independence before moving to recall Parliament.

Cameron said he would work with allies to defeat the terrorist group to “drain this poison from our society” and supports the United States’ decision to take military action.

 In a tweet from his official account, he called the apparent murder of Haines as “an act of pure evil.” “They are not Muslims,” he said. “They are monsters.” 

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

“David has been murdered in the most callous and brutal way imaginable by an organization which is the embodiment of evil,” the prime minister said. “We will hunt down those responsible and bring them to justice no matter how long it takes.

“David Haines was an aid worker. He went into harms way not to harm people but to help his fellow human beings in the hour of their direst need – from the Balkans to the Middle East.”

The prime minister added: “His burning desire to help others has cost him his life. The whole country, like his grieving family, can be incredibly proud of what he did and what he stood for in his humanitarian mission. David Haines was a British hero.”

The beheading of Haines comes after ISIS claimed responsibility for executing American journalists James Foley and Steven Sotloff. President Barack Obama said Saturday the U.S. would stand with Britain in the fight against the terror group.

"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," he said.

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