Story highlights Nuri al-Maliki vows Iraq will make its stand against ISIS in Samarra

Officials tell CNN 60% to 70% of province home to Samarra in ISIS hands

U.S. aircraft carrier sent to Gulf to give Obama "additional flexibility"

Iraqi commander tells how his battalion abandoned its post when ISIS advanced

Iraq's leader directed his troops to make their stand against advancing Sunni militants in a flashpoint city home to a revered Shiite mosque, an order that highlights the sectarian fighting tearing the country apart.

Prime Minister Nuri al-Maliki's order came as he sought to put new fire in the belly of his troops in the fight against the Islamic State in Iraq and Syria -- an al Qaeda splinter group known as ISIS -- that has seized a large swath of land in the north of the country and threatened to advance on the capital.

"Samarra will be the starting point, the gathering station of our troops to cleanse every inch that was desecrated by footsteps of those traitors," al-Maliki said in remarks broadcast Saturday.

Iraq's military claimed Saturday it had regained key northern territories, including most of Salaheddin province, which includes Samarra, from ISIS, a claim that conflicted with reports from security officials in Baghdad and Samarra, who told CNN that 60% to 70% of the province remains in the hands of ISIS.

The news came the same day U.S. Defense Secretary Chuck Hagel ordered the aircraft carrier USS George H.W. Bush into the Persian Gulf from the North Arabian Sea.

The order gives U.S. President Barack Obama "additional flexibility should military options be required to protect American lives, citizens and interests in Iraq," Pentagon press secretary Rear Adm. John Kirby said in a statement Saturday.

Battle in the north

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The militants from ISIS want to establish a caliphate, or Islamic state, in the region -- stretching from Iraq into northern Syria, where it has had significant success battling the forces of President Bashar al-Assad.

Their lightning advance in Iraq has been aided by support from many Sunnis who feel that the Shiite-dominated government has marginalized them.

ISIS seized Iraq's second-largest city, Mosul, earlier this week and have threatened to march on Baghdad.

Although they have not yet delivered on that threat, the militants' rapid advance -- and the total collapse of Iraq's security forces in the face of their assault on Mosul -- have rocked the government and alarmed its international allies, including the United States.

In Samarra, the Iraqi Prime Minister said thousands of Iraqis volunteers had stepped forward to fight against the militants.

"They (ISIS) believed that this is the beginning of the end, but we say, this is the beginning of their end, their defeat, because it sparked the passion and determination in all soldiers and officers, and in all Iraqi people," al-Maliki said.

The Prime Minister blamed the collapse of Iraqi security forces in the northern city of Mosul and elsewhere on confusion resulting from conspiracy and collusion, but also warned that all deserters would be held accountable.

Footage from Baghdad on Saturday showed volunteers climbing into buses outside an Iraqi army recruiting center in the city.

"The security situation in Baghdad is completely stable." Iraq's military spokesman Maj. Gen. Qassim Atta said the capital was safe. "The situation in Samarra is completely stable, and the troops are prepared for any terrorist plans."

Atta accused the media of false reporting, saying Iraqi troops along with volunteer fighters now control several town and cities north of Baghdad.

But conflicting reports emerged concerning security in the town of al-Dhuluiya, outside of Samarra, about 100 kilometers (62 miles) north of the Iraqi capital.

Government officials and state TV said Saturday that Iraqi security forces had taken control of the town, but security officials in Samarra and witnesses there told CNN the town is still under ISIS control.

If the witness accounts are true, it puts ISIS within striking distance of Samarra. The city is significant to Iraq's Shiites for its al-Askari mosque, and the Sunnis of ISIS have threatened to destroy any shrine they deem un-Islamic.

An attack on the mosque in 2006 was ground zero for the sectarian fighting that pushed the country to verge of civil war, and many fear another such attack would push Iraq to the breaking point.

Samarra authorities on Saturday found the bodies of 12 police officers dumped in an orchard in nearby Ishaqi. The bodies were shot and burned in al-Basateen area in Ishaqi, a predominantly Sunni town about 62 miles north of Baghdad, police officials said.

Police believe that ISIS fighters killed the police officers, but an investigation is ongoing.

Rouhani: We will consider request for help

Obama continues to mull his options in light of the militants' quick advance -- but has ruled out putting U.S. troops on the ground.

A senior security official in Baghdad told CNN on Friday that in recent days, Iran has sent about 500 Revolutionary Guard troops to fight alongside Iraqi government security forces in Diyala province.

However, Iranian officials, including President Hassan Rouhani, have 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.

Amid the conflicting reports, a U.S. official told CNN that the head of Iran's elite Quds force, Gen. Qassim Suleimani, was in Iraq this week.

While the details of what he was doing are unclear, he was believed to have been offering advice about how to stop the march of ISIS militants, the official said, on condition of anonymity in order to discuss the latest U.S. intelligence.

While leaders from Iran and the United States both want to see the militants thwarted, the U.S. State Department said Friday there were no discussions between the two countries about the situation in Iraq. The Suleimani visit was first reported by the New York Times

Commander tells of abandoning post

An Iraqi army commander who was in charge of a battalion of about 600 men told CNN how he had abandoned his post in northern Iraq after being alerted that ISIS fighters were pushing through.

The commander, who asked for the location where he was based not to be disclosed, said his soldiers had been instructed by brigade headquarters immediately to abandon their positions, grab what weapons they could and move toward the headquarters.

They did so, he said, leaving behind heavy weaponry and vehicles, including Humvees -- and with the ISIS militants hot on their heels. When they reached the headquarters, it was already overrun by ISIS.

The commander said his unit was predominantly Sunni, as is the population in that part of the country, and they had no desire to fight for the predominantly Shiite government of al-Maliki. ISIS has the support of the people, he said.

He predicted that if ISIS were to enter Baghdad, any Sunni soldiers there would defect, leaving only troops of Shiite origin to fight alongside Shiite militia groups, some of which were involved in the bloody sectarian strife that followed the U.S.-led invasion of Iraq in 2003.

Obama: Won't happen overnight

Pressure for the United States to provide military support to Iraq's struggling government has increased, with conservative Republicans blaming Obama for creating a security vacuum in 2011 by pulling out U.S. troops.

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.

Critics also say that Obama's unwillingness to provide significant military backing to opposition forces in Syria's civil war has contributed to the ability of ISIS to attack in Iraq.

Obama has blamed Iraq's political dysfunction for the failure of its troops to fight off the ISIS advance from the north to within about 60 miles of Baghdad on Friday, noting that there has been no shortage of U.S. help in terms of equipment and training.