Iraq's politicians are appealing to the international community to help battle Islamic State fighters as their dramatic push into the country's north continues. Here's what we know so far about IS and the situation in Iraq.
How is Australia involved in the Iraq crisis?
Prime Minister Tony Abbott has suggested Australia is prepared to send military forces to Iraq if that's what is needed to prevent genocide by the "murderous hordes" fighting for Islamic State.
The Australian government also says it's considering offering protection to Christians being targetted by Islamic insurgents in northern Iraq. A spokesman for Immigration Minister Scott Morrison told SBS 4,000 places have been made available in Australia's special humanitarian program for refugees offshore. The spokesman said the government is keeping a close watch on the situation in Iraq and Syria and will consider offering protection as part of its emergency response.
It's thought 60 Australians are fighting with Islamic State or offshoots in Iraq and Syria. Another 90 Australians are likely supporting them from back home.
Australia and the United States will take a joint proposal to the UN on tackling the growing threat of home-grown terrorists. The United States and Australia agreed to take concerns about the threat posed by jihadist foreign fighters in Syria, Iraq and elsewhere to the United Nations.
The issue was discussed at AUSMIN talks in Sydney with US Secretary of State John Kerry. Foreign Minister Julie Bishop says the US and Australia share a concern about their citizens fighting in conflicts around the world and becoming radicalised.
Ms Bishop said the concern about extremists returning home with terrorism skills was shared across the world. The discussion was spurred by images of a Sydney-raised boy holding the severed head of soldier in Syria.
What are other countries doing about IS?
Britain has begun airdropping food and water to thousands of civilians stranded on a mountain in northern Iraq after fleeing jihadist militants.
The United States carried out air strikes and aid drops as President Barack Obama vowed to help thousands of civilians besieged by jihadists on an Iraqi mountain.
US forces hit out on the campaign's second day to protect members of the Yezidi minority, many of whom have been stranded on Mount Sinjar since they fled IS attacks on their homes a week ago. President Obama had previously said the US was intervening to "prevent an act of genocide".
France and Britain announced that aid consignments of their own were imminent.
Why are the Yezidi being targeted by Iraqi jihadists?
Recently, IS militants managed to oust Pershmerga and Yezidi minorities, sparking an exodus said to be in the hundreds of thousands.
The IS militants are hostile to Shiite Muslims, Kurds, Christians and other groups who don't agree with their brand of Sunni Islam, but the Yezidi in particular are being targeted.
Numbering about 700,000 worldwide the Yezidi are a sect that combines elements of Islam and Zoroastrianism, an ancient Persian religion dating back to at least 600 B.C.
According to The International Business Times, there are around 500,000 Yezidi in Iraq, mainly in the north where IS have captured the towns of Zumar and Sinjar.
Ethnically the Yezidi are Kurdish, and are considered fellow Kurds up north.
Under Saddam Hussein's rule many Yezidi villages were wiped out as troops moved in on Iraq's Kurdistan region.
There are smaller Yezidi populations in Germany, Syria, Russia, Armenia and Georgia. The are around 500 Yezidi living in the US, according to the Joshua Project.
What is the Islamic State and where did it come from?
The Islamic State jihadist group, formerly known as ISIS, controls much of northwestern Iraq. Formed in 2013, IS is a jihadi Salafist militant group. It is virulently anti-democracy and sectarian – and also a seasoned militant operation with a transnational membership, to which, despite heavy losses, it is constantly recruiting. With key leaders who were prominent in the Iraqi insurgency in the 2000s, it is also well-armed and financed.
IS has shown the capacity to assimilate other extremist Sunni organisations, such as Salafiah al-Mujahidiah. The violence it perpetrates is in many ways broader than that wrought by other groups; it includes a wide array of attacks on humanitarian aid organisations, videoed beheadings, kidnappings and suicide attacks.
But IS’s desire to create a caliphate also tolerates no other armed group capable of challenging its jihadist credentials. This has seen the group disowned by al-Qaeda for harming others dedicated to the creation of an Islamic nation.
IS’s swift seizure of territory in Iraq in recent weeks was a shock given claims that they were in decline, and had been expelled from areas such as Deir Ez-Zor and Raqqa – claims that have turned out to be far wide of the mark. Evidently, under the leadership of Abu Bakr al-Baghdadi, IS have reformed and re-dedicated their efforts.
Who is the Islamic State's Abu Bakr al-Baghdadi?
Al-Baghdadi is thought to have been born Awwad Ibrahim al-Badri al-Sammari in the Iraqi town of Sammara, just north of Baghdad, in 1971.
He's believed to have studied in Baghdad, later fighting the United States occupation after 2003, under the al-Qaeda banner.
Later he would send an al-Qaeda emissary to Syria to from a key insurgent group there, Jabaht al Nusra,according to independent Australian Lebanese journalist Rania Abouzeid. Ms Abouzeid reports al Qaeda in Iraq refused him permission to merge Jabaht al Nusra with his own Iraqi al-Qaeda offshoot, ISIS.
And by early 2014 al Qaeda in Iraq would disown al-Baghdadi and his new group, who were gaining a reputation - even amongst jihadists - as a brutal band of fighters, with little mercy.
What led to the Islamic State's terrifying rise?
The group began as an offshoot of al-Qaida at the height of the Sunni insurgency in Iraq in 2006. It was subdued by an American counterinsurgency aided by Sunni tribes who had allied with the Iraqi state. But the outfit reemerged by 2009 in northern Iraq, laying the ground for its current takeover.
The ongoing chaos and civil war in neighboring Syria was a catalytic force: The group, then known as ISIS, was one of a hodgepodge of militant factions battling the forces of Syrian President Bashar Assad. But it steadily gained ground, holding sway over a stretch of territory in both countries, including the Syrian city of Raqqa, which functions as its de facto capital.
Within a space of months this summer, Islamic State fighters steamrolled through northern Iraq, capturing the city of Mosul, while rampaging toward Baghdad, further south, and north toward lands contested by the pesh merga of Iraq's largely autonomous Kurdish Regional Government.
All the while, the group consolidated power, formed practical alliances and captured funds and weaponry belonging to the Iraqi state. Its fighters are better equipped and more disciplined than many in the Iraqi army. As they unleashed horrors upon religious minorities caught in their conquests — attacking Christians, Yazidis, Shiites and earning comparisons to the ravages of Genghis Khan — they actually won praise from some living under their rule for good governance.
The declaration of a caliphate this summer signaled their delusional world-historic aims. But it sprang from very diligent strategic planning.