Media playback is unsupported on your device Media caption The BBC's Paul Wood met refugees who have fled to the Kurdish countryside 
 
 US President Barack Obama says his government is looking at "all options", including military action, to help Iraq fight Islamist militants. 
 
 But the White House also insisted it had no intention of sending ground troops. 
 
 The remarks came after the cities of Mosul and Tikrit fell to Sunni Islamist insurgents during a lightning advance. 
 
 The US has begun moving defence contractors working with the Iraqi military to safer areas. 
 
 "We can confirm that US citizens, under contract to the government of Iraq, in support of the US Foreign Military Sales (FMS) programme in Iraq, are being temporarily relocated by their companies due to security concerns in the area," state department spokesperson Jen Psaki said. 
 
 Several hundred were being evacuated from Balad air base to Baghdad, a US defence official told AFP. 
 
 Media playback is unsupported on your device Media caption Obama: "The US will do our part, but... it us up to the Iraqis as a sovereign nation to solve their problems." 
 
 Led by the Islamic State in Iraq and the Levant (ISIS), the insurgents are believed to be planning to push further south to the capital, Baghdad, and regions dominated by Iraq's Shia Muslim majority, whom they regard as "infidels". 
 
 Unconfirmed reports on Thursday said Iraqi forces had launched air strikes on Mosul and Tikrit targeting the militants. 
 
 Correspondents say that if ISIS can hold Mosul and consolidate its presence there, it will have taken a giant step towards its goal of creating an Islamist emirate that straddles Iraq and Syria, where insurgents control a large swathe of territory. 
 
 Fears of ISIS sparking a wider Sunni uprising have increased with reports that former Baath Party members loyal to Saddam Hussein have joined forces with the jihadists. 
 
 One resident in Tikrit, Saddam Hussein's former hometown, told the AP news agency that fighters raised posters of the former dictator after driving the army out. 
 
 The United Nations Security Council said on Thursday it unanimously supported Iraq's government and people in their "fight against terrorism". 
 
 Earlier it said the humanitarian situation around Mosul, from where up to 500,000 people have fled, was "dire and... worsening by the moment". 
 
 Analysis: Jeremy Bowen, BBC Middle East editor 
 
 If ISIS can hold Mosul and consolidate its presence there it will have taken a giant step towards its goal of creating an Islamist emirate that straddles Iraq and Syria. 
 
 It would be the most significant act by a jihadist group since al-Qaeda attacked the US on 11 September 2001. It could also lead to other changes on the borders Britain and France imposed on the Middle East a century ago, starting with break-up of Iraq on sectarian lines. 
 
 The success of ISIS can only make the turmoil in the Middle East worse. ISIS is an ultra extremist Sunni Muslim group. Its success will deepen the sectarian conflict between Sunnis and Shias that is already the most dangerous fault line in the Middle East. 
 
 Iran, which is a majority Shia Muslim country, shares a border with Iraq. It has a direct line to Iraq's Shia Muslim Prime Minister, Nouri Maliki, and close links with some Iraqi Shia militias. The Iranians could direct their proxies, and even their own special forces units, at ISIS. 
 
 That might end up further inflaming the anger of Iraqi Sunnis, who have already helped the advance of ISIS through Iraq. 
 
 US air strikes, if they happen, might do the same thing. Once again in the Middle East, the Americans have limited options. Its invasion and occupation of Iraq in 2003 helped create and strengthen jihadist groups. 
 
 Media playback is unsupported on your device Media caption Iraq's former PM Ayad Allawi says the country could be facing a break-up as a result of the insurgency led by Islamist militants 
 
 Insurgent advance 
 
 "There will be some short-term immediate things that need to be done militarily," Mr Obama told reporters at the White House as he met Australian Prime Minister Tony Abbott. 
 
 "I don't rule out anything because we do have a stake in making sure these jihadists are not getting a permanent foothold in Iraq, or Syria for that matter." 
 
 White House spokesman Jay Carney subsequently added that President Obama was referring to not ruling out air strikes. "We are not contemplating ground troops," he said. 
 
 Iraq's ambassador to the US, Lukman Faily, earlier told the BBC this was the "most serious situation" faced by the country in recent years. 
 
 Media playback is unsupported on your device Media caption Iraq state TV airs footage said to be airstrikes on the ISIS-held city of Mosul 
 
 Image copyright AP Image caption Iraqis gathered at the army's recruitment centre in Baghdad, after officials urged them to fight the militants 
 
 Image copyright AFP Image caption Footage allegedly showing captured vehicles of Iraqi security forces with the ISIS flag in Mosul 
 
 A parliamentary vote to grant PM Maliki emergency powers was delayed earlier after MPs failed to turn up. 
 
 Just 128 out of the 325 MPs were present for the vote. 
 
 Correspondents say the failure of the Iraqi parliament to achieve a quorum to vote on emergency powers says much about the fragmented state of Iraqi politics. 
 
 In the north of the country, Kurdish forces have claimed control of the oil city of Kirkuk, saying government forces have fled. 
 
 The Kurds - seen as a bulwark against the Sunni Muslim insurgents - have also been locked for years in a dispute with Baghdad over Kirkuk, seeking to incorporate it into their own autonomous area. 
 
 Media playback is unsupported on your device Media caption The BBC's Rami Ruhayem reports from Irbil in Kurdish-run northern Iraq, as an audio recording of ISIS spokesman Abu Muhammad al-Adnani is released 
 
 They are clearly happy to fill the vacuum left in Kirkuk, an area they historically claim as theirs, the BBC's Jim Muir reports from Kurdish-run Irbil. 
 
 Iraqi government forces slowed the insurgents' advance on Wednesday outside Samarra, a city just 110km (68 miles) north of Baghdad. 
 
 But reports have emerged of the rebels bypassing Samarra and seizing the town of Dhuluiya, 90km north-west of the capital. 
 
 Security in Baghdad has been stepped up after a video emerged of the militants threatening to march on the city. 
 
 ISIS in Iraq 
 
 Image copyright AP Image caption An Islamist fighter near a burning Iraqi army Humvee in Tikrit 
 
 The Islamic State in Iraq and the Levant (ISIS) has 3,000 to 5,000 fighters, and grew out of an al-Qaeda-linked organisation in Iraq 
 
 ISIS has exploited the standoff between the Iraqi government and the minority Sunni Arab community, which complains that Shia Prime Minister Nouri Maliki is monopolising power 
 
 It has already taken over Ramadi and Falluja, but taking over Mosul is its greatest achievement 
 
 The organisation is led by Abu Bakr al-Baghdadi, an obscure figure regarded as a battlefield commander and tactician who was once the leader of al-Qaeda in Iraq, one of the groups that later became ISIS. 
 
 Critical test ahead for Iraq 
 
 Six things that went wrong for Iraq 
 
 How did Iraqi militants take over Mosul? 
 
 In pictures: Iraq cities attacked ||||| Story highlights The Iraqi air force killed more than 200 ISIS militants, according to Iraq state TV 
 
 U.S. may try to speak directly to Iran about deteriorating Iraq situation, senior U.S. officials say 
 
 Dozens of U.S. military personnel arrive at U.S. Embassy, a U.S. official says 
 
 Photos appearing online appear to show ISIS fighters executing Iraqi security forces 
 
 The Iraqi air force struck back at the militant group ISIS , the Islamic State in Iraq and Syria, killing more than 200 militants, Iraqi state TV reported Monday morning. The air raids took place in Saqlawiyah, northwest of Fallujah, according to a graphic run by state TV. 
 
 ISIS has been ruthlessly fighting to take control of Iraq and has apparently posted chilling photos on jihadi Internet forums seeming to show the executions of Iraqi security forces. 
 
 CNN cannot independently confirm the authenticity of the images purportedly posted by ISIS . CNN is examining the terrain in the images, some of the signage on buildings in several of the pictures and the uniforms of the apparent victims. Those details suggest the photos are real and were taken in Iraq. 
 
 A caption on some of the images reads: "apostates heading to their hole of doom." 
 
 ISIS, an al Qaeda splinter group, wants to establish a caliphate, or Islamic state, that would stretch from Iraq into northern Syria. The group has had substantial success in Syria battling Syrian President Bashar al-Assad's security forces. 
 
 On Friday, a tweet on what was claimed to be an ISIS Twitter account claimed that its members killed at least 1,700 Shiites. CNN was unable to verify the authenticity of the account, and the account appeared to have been taken down Sunday. 
 
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 In a statement, the U.S. State Department condemned the claim by ISIS, also known as ISIL, the Islamic State of Iraq and the Levant. 
 
 "The claim by the Islamic State of Iraq and the Levant (ISIL) that it has massacred 1700 Iraqi Shia air force recruits in Tikrit is horrifying and a true depiction of the bloodlust that these terrorists represent. While we cannot confirm these reports, one of the primary goals of ISIL is to set fear into the hearts of all Iraqis and drive sectarian division among its people," part of the statement read. "Terrorists who can commit such heinous acts are a shared enemy of the United States, Iraq, and the international community. " 
 
 The militants' quick advance in Iraq has been helped by many Sunnis who feel that the Shiite-dominated government has marginalized them. 
 
 ISIS seized Iraq's second-largest city, Mosul, last week and has threatened to march on Baghdad, Iraq's capital and largest city. 
 
 But "Mosul didn't fall," a defiant Iraqi Prime Minister Nuri al-Maliki told military leaders in Baghdad in a speech televised Sunday on state TV. "The ones who have fallen are the politicians who have bet against Iraq." The Prime Minister said, "We will not allow anyone to divide the Iraqi people." 
 
 Al-Maliki called on his top brass and soldiers to march and fight against ISIS, while criticizing Iraqi politicians conspiring against their homeland and Iraqi soldiers who have refused to continue to fight when confronted by ISIS. 
 
 "We will march on every inch, with all our weapons, with all our will and faith, so we can liberate and cleanse every inch of Iraq -- from the southernmost point to the furthest point in the north," he exhorted the military leaders. 
 
 Despite al-Maliki's bold statements, ISIS accumulated several victories across Iraq on Sunday. 
 
 The northwest Iraqi city of Tal Afar fell to ISIS, according to Iraqi Gen. Mohammed al-Quraishi. Many Tal Afar residents -- ethnic minority Shiite Turkmen -- fled the fighting north toward Iraq's Kurdish region. Tal Afar is in Nineveh province, midway between the country's border with Syria and Mosul, north of Baghdad. 
 
 Before Iraqi security forces lost Tal Afar, several mortar rounds landed on a busy area in the town and killed at least seven and wounded 33 people, security officials in Baghdad and Tal Afar told CNN. 
 
 Also Sunday, ISIS gained control of two villages in Adhaim, in its first push into Diyala province, northeast of Baghdad. 
 
 On top of that, Iraqi security forces and gunmen believed to be ISIS clashed near al-Khalis, about 18 miles from Diyala's capital, Baquba, al-Khalis police officials told CNN. Three mortar rounds landed near a recruitment center opened recently for volunteers to help the Iraqi army fight against ISIS. 
 
 Baquba is about 37 miles northeast of Baghdad. Baquba is an ethnically-mixed city, though Sunnis represent a slight majority. 
 
 Given Baquba's proximity to Baghdad, if Baquba were to fall, it could give ISIS militants three-pronged access to Baghdad -- from Anbar province to the west, Ninevah and Salahuddin provinces to the north and from Diyala province from the northeast. 
 
 Meanwhile, on Sunday, CNN Senior International Correspondent Arwa Damon was in the Iraqi Kurdish province of Kirkuk, where last Thursday militants took control of two villages. 
 
 She asked the local governor, Dr. Najmaldin Karim, whether the United States should launch airstrikes to help fight back ISIS. 
 
 "I think they know how to do it, but blanket bombing is not going to work here," Karim said, explaining that that approach ignores the fact that ISIS is too blended into the civilian population in Kirkuk and innocent people could die. But there should be targeted bombing in both Iraq and Syria, he said. 
 
 "I don't think anyone is safe from these people," said Karim. 
 
 Partial staff relocation at U.S. Embassy 
 
 Between 50 and 100 U.S. Marines and U.S. Army personnel have arrived at the U.S. Embassy in Baghdad, a U.S. official told CNN on Sunday. 
 
 A U.S official acknowledged to CNN that the additional embassy security personnel being added include U.S. Marines who specialize in embassy protection during high-threat conditions. 
 
 The U.S. invaded Iraq in 2003. American military forces ended their withdrawal from the country in December 2011. 
 
 At the time of the U.S. drawdown, Iraq's leadership had agreed that a residual U.S. military presence was desirable, but the talks broke down over the prickly issue of legal immunity for U.S. troops in Iraq. 
 
 The Obama administration had said any deal to keep U.S. troops in Iraq beyond the withdrawal deadline would require a guarantee of legal protection for American soldiers. But the Iraqis refused to agree to that, opening up the prospect of American troops being tried in Iraqi courts and subjected to Iraqi punishment. 
 
 This week, President Barack Obama continued to consider options with regard to the situation in Iraq but ruled out sending troops into the country. 
 
 On Sunday, U.S. State Department spokeswoman Jen Psaki said that some U.S. security personnel will be added to the staff at the U.S. Embassy in Baghdad and other staff members will be temporarily relocated to consular offices in Basra and Irbil and to the Iraq Support Unit in Amman, Jordan. 
 
 A "substantial majority of the U.S. Embassy presence in Iraq will remain in place," Psaki said in a statement, and "the Embassy will be fully equipped to carry out its national security mission." 
 
 Pentagon Press Secretary Rear Adm. John Kirby said that a "small number of Defense Department personnel" are augmenting State Department security assets in Baghdad. Kirby said that the relocation of some embassy personnel is being done with commercial, charter and State Department aircraft flights. 
 
 The U.S. military can airlift people if the State Department asks for that, Kirby said. 
 
 The State Department is warning U.S. citizens against "all but essential travel to Iraq." The official travel warning says U.S. citizens in Iraq "remain at high risk for kidnapping and terrorist violence." 
 
 While that continues, Iran has recently entered the fray, according to a senior security official in Baghdad who spoke to CNN on Friday. That official said that in recent days, Iran has sent about 500 Iranian Revolutionary Guard troops to fight alongside Iraqi government security forces in Iraq's Diyala province. 
 
 However, Iranian officials, including President Hassan Rouhani , denied reports that some of its elite forces are in Iraq to help bolster al-Maliki, a fellow Shiite. 
 
 "If the Iraqi government wants us to help, we will consider it," Rouhani said, according to an English translation of his remarks Saturday in Farsi by state-run Press TV. 
 
 But, he said, "so far they have not asked specifically for help," and added that Iran could give strategic guidance if requested. 
 
 The Obama administration is exploring possible direct talks with Iran over the deteriorating situation in Iraq, two senior U.S. officials tell CNN. 
 
 Both officials ruled out any type of teaming up with Iran because the United States and Iran don't have a lot of common interests -- other than a stable Iraq. 
 
 The United States is wary of furthering Iran's already considerable influence in Iraq. The Shiite Iranian regime is al-Malaki's closest ally in the region. Additionally the administration is concerned appearing to team up with Iran would both alienate Iraq's Sunni majority and worry Sunni allies of the United States in the region. 
 
 The State Department statement said the United States "will do its part to help Iraq move beyond this crisis," and a senior State Department officer told CNN that Kerry spoke to his counterparts from Jordan, the UAE, Saudi Arabia and Qatar to discuss the threat posed by ISIS. 
 
 The administration has not yet determined what the mechanism would be for talking to Iran, the senior U.S. officials said. 
 
 Ex-U.S. ambassador: Kerry should go to Iraq 
 
 On Sunday U.S. Sen. Lindsey Graham argued on CNN's "State of the Union" for more intervention in Iraq. 
 
 The South Carolina Republican, a frequent critic of the Obama administration's approach to foreign policy, called Obama "stubborn-headed," "delusional" and "detached" over his decision on how to react to the unfolding crisis. 
 
 "Time is running out to turn this around," Graham said. "Get involved with air power. Stop the march toward Baghdad. Deal with Syria. But get a new government (in Iraq) in place as quickly as you can that will bring the Iraqis back together for a counteroffensive." 
 
 Ryan Crocker, the U.S. ambassador to Iraq from 2007 to 2009, told CNN's Fareed Zakaria on Sunday that he thinks Secretary of State John Kerry should fly to Iraq immediately. 
 
 "We need the secretary of state out there in Baghdad right now," Crocker said. "We need the President on the phone to the Iraqi leadership because the reality is the Iraqis are not in a position ... they were not in a position when I was there, they are not in a position now, to work out hard compromises on their own." 
 
 The United States is the "middleman among Sunni, Shia and Kurds," Crocker said. "Ambassadors can go just so far." 
 
 Crocker, now the dean of the George Bush School of Government & Public Service at Texas A&M University, said he would support "very carefully targeted airstrikes" in conjuction with high-level diplomacy. 
 
 "We have got to help the Iraqis come together," Crocker urged, "in a unified fashion to confront a common threat."
– The US rebuffed Iraq's request for airstrikes as insurgents gained strength, but American drones were already collecting intelligence on the militants. The secret drone program, carried out with the consent of the Iraqi government since last year, failed to predict the rapid advance of militants who have now seized several cities, officials tell the Wall Street Journal. "It's not like it did any good," one US official says. President Obama says "all the options" are being considered to help Iraq and while the use of ground troops has been ruled out, officials are considering expanding the drone program. The al-Qaeda-linked Islamic State of Iraq and Syria militants have vowed to take the fight to Baghdad, and although the capital is not expected to fall, Americans in Iraq are keeping an eye on the exit. Officials say they have stepped up plans for the evacuation of the US Embassy in Baghdad, and the BBC reports that American defense contractors working with the Iraqi military are being shifted to safer areas. Hundreds of contractors "are being temporarily relocated by their companies due to security concerns in the area," according to a State Department spokeswoman.