Iraqi soldier Bassil Hassan says he wept as he abandoned his base in the face of a Sunni militant advance and is desperate to redeem himself by returning to the fight.

He stands outside the Iraqi Airways office in the northern city of Arbil, clamouring for a ticket on any plane back to Baghdad to rejoin his unit.

He is one of many Iraqi army soldiers who left their posts, clearing the way for Sunni militants, including jihadists from the Islamic State of Iraq and Levant (ISIL), to seize major cities.

"I've been in the army for five years, and I've never withdrawn without a fight," says Hassan.

"Before we left, we were weeping. We feel so ashamed, because we didn't fight, we were defeated without firing a single shot."

He says soldiers in his unit in Kirkuk province began deserting individually in the hours after the northern city of Mosul fell and militants were reported to be entering the province.

His commander summoned the troops and said they could leave if they wanted.

"Then 10 minutes later he came back and said there's an order from Baghdad to leave, put on civilian clothes and go back to your families."

Security forces in Mosul and surrounding Nineveh province, as well as Salaheddin and Kirkuk largely wilted when faced with the militant onslaught, which began late June 9 and overran swathes of territory north of Baghdad.

Soldiers and police have regrouped in recent days, though insurgents have still made progress, particularly in western Iraq.

- Back to duty -

Now, with the federal government in Baghdad having ordered the forces to return to duty immediately, Hassan and others are eager to prove their mettle.

Hussein Ali, a 28-year-old army mechanic, was based in Mahmudiyah, south of Baghdad.

He was on leave in his hometown of Kirkuk when the militant advance began, and the checkpoints they have established on the road to Baghdad made it impossible for him to return.

"I'm not one of those who ran away, I was on leave," he says.

"Now my boss is accusing me of going absent" without leave, he adds, his voice rising at the accusation.

"I'm trying to get a (plane) ticket, but they say there are no seats."

He says soldiers who abandoned their posts in places like Mosul and Tikrit, which are now under militant control, are "traitors," and insists he is eager to go back.

"I want to support the fight against the terrorists. I want to play my role."

Nearby is 26-year-old Mustafa Hussein, an electrical engineer with the army, who was based in Kirkuk.

He says the men in his technical contingent were forced to leave their station when troops from the Kurdish forces known as the peshmerga arrived.

"We didn't withdraw," he said.

"The peshmerga came and said we were going to cooperate as a joint force, but then problems started with them, they even pointed their weapons at us, and then they kicked us out."

- Bitterness towards Kurds -

He is bitter at the Kurdish troops, saying he and his colleagues would have been happy to cooperate with them and contribute their expertise.

But he also says his superior in Baghdad encouraged him to leave.

"We asked the commander, who was in Baghdad, to help us and give us weapons but he refused and told us to go home."

For the last four days, he has been coming to the airline office to try and find a flight back, with no success.

More than half a million Iraqis fled their homes in cities that fell to militants, and many of them are trying to fly south to areas that are still safe, for now.

"As soon as there is a seat, I will go to Taji base, and get back to work," Hussein says, referring to a base north of Baghdad.

Hassan, like many withdrawing troops, left his weapon behind, but he expects to get a new one when he rejoins his unit.

"I want to return to my brothers because I belong to the army," he says.

"My unit is going to be reconstituted in Baghdad... We will go and fight wherever they send us."

"ISIL is a disease and hopefully Iraq can be cured of this disease."