In a bid to reassure the situation is under control, Iraqi state TV shows video of hundreds of volunteers standing in front of a military recruiting station Sunday. They interviewed military commanders to reinforce the message that popular enthusiasm to fight Sunni militants from the al-Qaida-linked Islamic State of Iraq and the Levant (ISIL) is strong.
But it is not immediately clear whether Iraqi government forces are gaining or losing ground.
Eyewitness reports and information on rival television networks are contradictory.
Iraqi Prime Minister Nouri al-Maliki lashed out at media organizations on Friday for allegedly “distorting the truth.”
The government cut Internet connections Sunday, in another sign of nervousness.
Iraqi government forces are digging trenches outside the northern entrances of the capital Baghdad, as worries grow that advancing Sunni militants will attack the city.
Meanwhile, the U.S. government has announced that in view of the ongoing violence it is relocating some diplomatic personnel, but will keep its embassy in Baghdad open and operating.
"Some additional U.S. government security personnel will be added to the staff in Baghdad; other staff will be temporarily relocated.... Overall, a substantial majority of the U.S. Embassy presence in Iraq will remain in place and the Embassy will be fully equipped to carry out its national security mission.," said a statement by the State Despartment.
A top government official says Iraqi forces have "regained the initiative" in their fight against Sunni militants who have seized large parts of the country and vow to overrun Baghdad.
The prime minister's security spokesman, Lt. General Qassem Atta, told reporters on Sunday that Iraqi forces have killed 279 "terrorists" since Saturday.
The military also claims it has inflicted heavy losses on militants fighting for control of the key town of Tal Afar, near the Syrian border.
The government's claim and casualty numbers are hard to verify. But Iraqi forces and Shiite volunteers are starting to regroup and bolster their defenses, especially around Baghdad.
Many government fighters abandoned their positions and left their weapons and vehicles behind last week as the militants seized territory in the north.
Residents leave Mosul
Asharqiya TV showed long lines of hundreds of vehicles, which it claimed continue to flee Mosul.
A Kurdish local official said on Sunday that he expected the number of refugees fleeing violence from Mosul to Arbil to increase, Reuters reported.
An estimated 500,000 Iraqis have already fled Mosul, home to some 2 million people, and the surrounding province, the International Organization for Migration said.
Sunni militants also reportedly blew up two churches inside the city and many, if not all, remaining Christian residents of the city have reportedly fled.
Baghdad's forces will be joined by a flood of volunteers, urged on by a call to arms from top Shi'ite cleric Grand Ayatollah Ali al-Sistani.
A recruitment center for such volunteers at the town of Khales in central Iraq came under mortar attack on Sunday, leaving six people dead, including three Iraqi soldiers, police and a doctor told AFP.
While thousands of Shi'ite volunteers turned out in government-held areas to join the Iraqi military, some reports say many Sunnis were reportedly joining the militants and their allies.
In Cairo, Arab League deputy head Ahmed Ben Helli told a news conference the group's ministerial council is “supporting the Iraqi government's effort to defeat the terrorists.”
But Helli urged the country's fractious leaders to “overcome their political and religious differences ... and to form a united government.”
Also on Sunday, ISIL posted graphic photos online that appear to show its fighters massacring dozens of captured Iraqi soldiers, according to an AP report.
The pictures on a militant website appear to show ISIL masked fighters loading the captives, dressed in civilian clothes, onto flatbed trucks before forcing them to lie face-down in a shallow ditch with their arms tied behind their backs.
The final images show the bodies of the captives soaked in blood after being shot.
The captions of the photos said the killings were to avenge the killing of an ISIL commander, Abdul-Rahman al-Beilawy, whose death was reported by both the government and ISIL shortly before the al-Qaida splinter group's lightning offensive.
Iraq's top military spokesman, Lieutenant General Qassim al-Moussawi, confirmed the photos' authenticity and said he was aware of cases of mass murder of captured Iraqi soldiers in areas held by ISIL, the AP reported.
Most of the soldiers who appear in the pictures are in civilian clothes. Some are shown wearing military uniforms underneath, indicating they may have hastily disguised themselves as civilians to try to escape.
The captions did not provide a date or location, but al-Moussawi said the killings took place in Salahuddin province.
State Department spokeswoman Jen Psaki called the images horrifying and a true depiction of the bloodlust these terrorists represent.
VOA's Edward Yeranian contibuted to this report from Cairo. Some information provided by Reuters, AFP and AP.