Grand Ayatollah Ali al-Sistani, Iraq's most-senior Shia cleric, has called on Iraqis to take up arms against Sunni fighters advancing towards Baghdad, prompting an immediate response from hundreds who volunteered to bolster the capital's defences.
Sistani issued the call to arms on Friday to defend Iraq against the offensive spearheaded by the armed group the Islamic State of Iraq and the Levant (ISIL), which had gained more ground in the country overnight by seizing the strategically important towns of Jalulah and Saaiydiyah.
"Citizens who are able to bear arms and fight terrorists, defending their country and their people and their holy places, should volunteer and join the security forces to achieve this holy purpose," Sistani's representative announced on his behalf during Friday prayers in the Shia shrine city of Karbala.
"He who sacrifices for the cause of defending his country and his family and his honour will be a martyr," he added.
The elderly Sistani, who rarely appears in public, is highly influential in the Shia Muslim world and is revered by millions.
Shortly after Sistani made his appeal, more than a thousand volunteers from Karbala made their way down to an army camp in the city of Taji, about 30km north of Baghdad.
The Associated Press news agency reported that they were set to take part in a one-day training course before being deployed to fight alongside Iraqi troops.
ISIL fighters have taken over a huge swathe of predominantly Sunni-Arab territory in northern and north-central Iraq since launching their offensive in the country's second city, Mosul, on Tuesday. They have since pushed south into ethnically divided Diyala province, towards Baghdad.
On Friday, they were fighting pro-government forces near Muqdadiyah, just 80km from Baghdad city limits.
Al Jazeera's Omar Al Saleh, reporting from Baghdad, said the air force was slowing down ISIL's advances.
"Army helicopters have fired missiles at targets in the city of Tikrit, north of Baghdad. We heard that one of the targets was a mosque but this has not yet been confirmed by officials.
"ISIL is now in control in the northeastern and the northwestern parts of the city of Samarra and in a small village in another part of Salah al-Din province. But the government is sending reinforcements and is slowing down their advances.
"We also heard that the first wave of volunteers has reached Samarra to protect the holy shrines in the city."
Meanwhile, in northern Iraq, Kurdish security forces have moved to fill the power vacuum caused by the retreating Iraqi forces - taking over an air base and other posts abandoned by the military in the ethnically mixed city of Kirkuk.
New security plan
Rupert Colville, the spokesman for the UN human rights office, told journalists in Geneva that the number of people killed in recent days may run into the hundreds, and that the number of wounded could approach 1,000.
The United Nations reported a spate of summary executions by ISIL fighters in its campaign.
|ANALYSIS: Military analyst Major Charles Heyman
US President Barack Obama said he was exploring all options to save Iraq's security forces from collapse.
One option under consideration is the use of drone strikes, such as those controversially deployed in Afghanistan, Pakistan and Yemen, a US official told the AFP news agency.
The Iraqi Interior Ministry said it had adopted a new security plan for Baghdad to protect it from the advancing fighters.
"The plan consists of intensifying the deployment of forces, and increasing intelligence efforts and the use of technology such as [observation] balloons and cameras and other equipment," ministry spokesman Brigadier General Saad Maan said.
"We have been in a war with terrorism for a while, and today the situation is exceptional."