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."