Soldiers armed with shovels are digging in just 25 kilometres north of Baghdad as others man new checkpoints, bolstering the Iraqi capital's defences against a militant assault.
A major militant offensive launched on Monday, spearheaded by the Islamic State of Iraq and the Levant (ISIL) group but also involving supporters of executed dictator Saddam Hussein, has overrun a large chunk of northern and north-central Iraq.
The advance swept to within less than 100km of the capital, raising fears among residents that the city itself would be next, though militants have since been pushed back by security forces in areas further north, making an assault on Baghdad appear less likely.
ISIL spokesman Abu Mohammed al-Adnani has vowed its fighters would press on to Baghdad and Karbala, a city southwest of the capital that is considered one of the holiest sites in Shi'ite Islam.
Top Shi'ite cleric Grand Ayatollah Ali al-Sistani on Friday urged Iraqis to take up arms against the Sunni militants.
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Trucks carrying hundreds of volunteers were among a large number of vehicles passing through the key main checkpoint north of Baghdad, as security forces carried out spot checks.
The volunteers sang patriotic songs as they were driven to a nearby training centre.
Security forces performed poorly when the militant onslaught was unleashed, but they now appear to be recovering from the initial shock and have begun to regain ground.
They are regrouping despite scenes of disarray in the early days of the offensive, when soldiers shed their uniforms for civilian clothes and abandoned weapons and other equipment.
And they have retaken areas north of the capital that were among the closest militants got to Baghdad, officers said.
