Clerics pleaded with Iraqis to defend their country yesterday after fighters who have seized large swathes of the nation’s heartland captured two more towns north-east of Baghdad.

Sheik Abdul-Mahdi al-Karbalaie told worshippers at Friday prayers that it was their civic duty to confront the threat.

He represents Grand Ayatollah Ali al-Sistani, the senior Shi’ite spiritual leader in Iraq.

“Citizens who can carry weapons and fight the terrorists in defence of their country, its people and its holy sites, should volunteer to join the security forces,” Mr Karbalaie said.

Prime Minister Nouri al-Maliki’s government has failed to form any coherent response after Islamic State of Iraq and the Levant (Isis) fighters overran Mosul, Tikrit and smaller communities, as well as military and police bases.

Gunmen entered and took two more towns late on Thursday, driving unhindered in machine-gun-mounted pick-ups into Sadiya and Jalula in Diyala province.

Iraqi soldiers abandoned their posts without resistance.

Residents of Jalula said the fighters had issued an ultimatum to the soldiers not to resist and to give up their weapons in exchange for safe passage.

UN human rights office spokesman Rupert Colville said that the number of people killed in recent days may run into hundreds and the number of wounded could approach 1,000.

Isis has vowed to march on Baghdad, but with its large Shi’ite population the capital would be a more difficult target.

So far the militants have stuck to the Sunni heartlands, where discrimination and mistreatment has already alienated people from Mr Maliki’s government.

But Baghdad authorities have tightened security around the capital nevertheless.

Three plane-loads of US contractors were evacuated from Balad air base north of Baghdad on Thursday and US President Barack Obama said Iraq needed more help, but did not specify what he would be willing to provide.

However, senior US officials said Washington is considering drone strikes.

The US is already flying unmanned aircraft over Iraq for intelligence purposes.

“We do have a stake in making sure that these jihadists are not getting a permanent foothold in either Iraq or Syria,” claimed Mr Obama.