Horrifying footage has emerged showing Sunni insurgents of the Islamic State of Iraq and the Levant (Isis) beheading a police officer.
In a shocking piece of footage - too graphic to publish - fighters are seen knocking on the door of a Sunni police major in the dead of night before they blindfold and cuff him.
They then carve off his head with a knife in his own bedroom as religious hymns are played in the background.
After the decapitation, the militants took a picture of the officer's head and posted it on Twitter with the comment: "This is our ball. It's made of skin #WorldCup."
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The brutal act has sparked outrage on Twitter.
ISIS behead an Iraqi and tweet this is our football it's made of skin... God have mercy. Where are Western 'powers' when you need them?— Zed Grrdaisy (@ZedGrrdaisy) June 13, 2014
God help us!! Muslim terrorists
‘This is our ball’: Iraqi jihadis cut off head for World Cup tweet— FátimaⓂ️ (@backatone000) June 13, 2014
Isis insurgents took control of Mosul, Iraq's second largest city, this week displacing hundreds of thousands of people.
Shortly afterwards, the militants imposed a strict set of Sharia laws on the citizens of Nineveh province, urging leaders not to "work with [the Iraqi] government and be traitors."
Isis has vowed to march on Baghdad.
The Iraqi government has asked for United States support to fight back against Isis, but President Barack Obama is still contemplating an American response to the sudden crisis.
He has vowed that the US will not be "dragged back" into military action in Iraq as long as leaders in Baghdad refuse to reform a political system that has left the county vulnerable to a fast-moving Islamic insurgency.
The US president ruled out the possibility of putting American troops on the ground in Iraq, but said he was considering a range of other options drawn up by the Pentagon.
Meanwhile, thousands of Iraqi civilians are joining government forces to fight against the insurgents.
The country's top Shia cleric, Grand Ayatollah Ali al-Sistani, used Friday's prayers to call for those "capable of carrying arms" to standing up to the Sunni militants, who took two more towns overnight and reportedly fighting just 50 miles from Baghdad.
Britain, meanwhile, is to give £3 million of aid to Iraq as the first step in dealing with the humanitarian consequences of the bloody insurgency by Islamist extremists.
International Development Secretary Justine Greening said the initial tranche of emergency cash would allow agencies to supply water, sanitation, medicine, hygiene kits and basic household items.