A spokesman for the Islamic State (IS) group, rampaging through northern Iraq, has warned that they will "humiliate the United States" and "raise the flag of Allah in the White House".

"I say to America that the Islamic Caliphate has been established," said Abu Mosa, spokesman for the group formerly known as the Islamic State of Iraq and the Levant (Isis).

"Don't be cowards and attack us with drones. Instead send your soldiers, the ones we humiliated in Iraq."

"We will humiliate them everywhere, God willing, and we will raise the flag of Allah in the White House," he added.

The comments were made in the first installment of a new documentary, entitled 'The Spread of the Caliphate: The Islamic State', by Vice Media who obtained exclusive access to the terror group.

The video follows the militants around the group's newly-created "Caliphate" in the Syrian city of Raqqa.

The group have grand ambitions of extending their caliphate across the Middle East but their threat to Americans came before US President Barack Obama's authorisation of strikes against the Islamist fighters in Iraq.

Obama said that he would not send troops back into Iraq but would launch aerial strikes that target the Sunni militants to prevent the slaughter of religious minorities and the threat to US interests.

Nearly 100,000 Christians have been forced out of Qaraqosh - Iraq's biggest Christian town - by the group while the Yazidi Kurds face a humanitarian crisis after 200,000 fleed the town of Sinjar, 50,000 into the barren Sinjar mountains at risk of starvation and dehydration.

"To stop the advance on Erbil, I've directed our military to take targeted strikes against Isis [IS] terrorist convoys should they move toward the city," he said in a speech at the White House.

"The only lasting solution is reconciliation among Iraqi communities and stronger Iraqi security forces."

In June, IS captured large swathes of northern Iraq such as the cities of Mosul and Tikrit and now have their sights set on Erbil, the capital of the autonomous Kurdistan region.