Updated at 9:38 a.m. ET

Al-Qaida-linked Sunni militants continued their march across the country, and a representative of the country's most revered Shiite cleric urged Iraqis to defend their nation, increasing the possibility of sectarian strife in Iraq.

Meanwhile, Kurdish fighters filled the vacuum created by fleeing Iraqi forces, and pressure built on President Obama to take action in Iraq.

Fighters from the Islamic State of Iraq and Syria, a Sunni group so radical that al-Qaida disowned it, seized Mosul and Tikrit this week.

Today, Iraqi officials told The Associated Press that the Islamists entered two towns in Diyalah province. One of those towns is Jalula, 80 miles northeast of Baghdad; the other is Sadiyah, 60 miles north of the capital.

The gains are significant because while Mosul and Tikrit are Sunni-dominated, Diyalah is ethnically mixed. But what the fall of Jalula and Sadiyah have in common with the other two cities is that Iraqi forces showed little to no resistance.

NPR's Alice Fordham, who is reporting from the country, spoke to Ali Yasser Ali, a police officer who worked alongside the Iraqi army in Mosul. He said the people of Mosul refused to cooperate with security forces.

"We asked why they wouldn't agree to work with us. Why?" he told Alice through an interpreter. "They said we are not humans. We are monsters."

Alice notes that Ali is Shiite while most people in Mosul are Sunni — a sectarian division that has come into sharp relief in Iraq. She also spoke to Farma Khalaf, a Sunni soldier, who told her Sunnis had reason to hate the Shiites.

"This is a failing system," he said in Arabic.

He says he saw Shiite soldiers promoted ahead of him, and Sunnis – including women - from the region detained without reason.

Here's more from Alice's story:

"Seeing swaths of Iraq slip under the control of Sunni militants in the last week has seemed startling and swift. But security forces seem disillusioned, and they don't see the point of fighting the al-Qaida offshoot known as ISIS – the Islamic State of Iraq and Syria because that group has the support of the local Sunni population."

ISIS militants have support from local Sunni tribes as well as people loyal to former President Saddam Hussein, whom the U.S. ousted with its invasion in 2003. The Islamists' stated goal: Baghdad. They have said they will impose Shariah law in the areas they have captured. Here's more from The Associated Press:

"A video posted online showed Islamic State fighters holding a parade in a Mosul neighborhood, with many of the gunmen sporting armored vehicles and American-made Humvees seized from Iraqi army and police."A fighter using a loudspeaker urged the people to join the militant group 'to liberate Baghdad and Jerusalem.' The Islamic State's black banners adorned many of the captured vehicles. Some in the crowd shouted "God is with you" to the fighters."The video appeared authentic and consistent with AP reporting of the events depicted."

The AP also reported that Shiite cleric Sheik Abdul-Mahdi al-Karbalaie, who represents Grand Ayatollah Ali al-Sistani, told worshippers today that it's their duty to fight for their country.

"Citizens who can carry weapons and fight the terrorists in defense of their country, its people and its holy sites should volunteer and join the security forces," al-Karbalaie said.

Sistani is the most revered Shiite spiritual leader in Iraq.

So far, much of the resistance to the Sunni fighters has come from the Kurds. Kurdish Peshmerga fighters have taken key portions of the oil-rich and strategically important city of Kirkuk. Those positions had been abandoned by government troops. The AP notes, "Their role is a potential point of friction because both Sunni and Shiite Arabs are wary of Kurdish claims on territory."

Iraqi Prime Minister Nouri al-Maliki has asked parliament to declare a state of emergency, a measure the legislative body is still discussing. For months, his government has asked the U.S. for help against the militants.

In Washington, pressure mounted on President Obama to take action in Iraq, which U.S. troops left in 2011. House Speaker John Boehner accused Obama of "taking a nap" on the issue. The president said he was considering all options.

"We do have a stake in making sure that these jihadists are not getting a permanent foothold in either Iraq or Syria, for that matter," Obama said on Thursday.

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