Jihadists were pushing towards Baghdad yesterday after capturing a town just hours to the north, as the US mulled air strikes in a bid to bolster Iraq's collapsing security forces.
With the militants closing in on the capital, forces from Iraq's autonomous Kurdish region took control of Kirkuk, an ethnically divided northern city they have sought to rule for decades against the objections of successive governments in Baghdad.
Kirkuk Governor Najm al-Din Karim said Kurdish forces had filled in gaps left by Iraqi soldiers who withdrew from their positions in the province.
Iraqi Foreign Minister Hosyhar Zebari acknowledged the security forces which Washington invested billions in training and equipping before withdrawing its own troops in 2011, had simply melted away.
Washington found rare common cause with its longtime foe Tehran, with both voicing dismay at the Sunni extremists' advance and pledging to boost aid to Iraq's beleaguered Shia prime minister.
The militants, who have swept up a huge swathe of predominantly Sunni Arab territory in northern and north-central Iraq since launching their offensive in second city Mosul late on Monday, advanced into ethnically divided Diyala province.
The insurgents captured the town of Dhuluiyah just 90 kilometres from Baghdad, army officers said, as they pushed into a province whose mixed Arab and Kurdish and Sunni and Shia population has made it a byword for violence ever since the 2003 overthrow of Sunni Arab dictator Saddam Hussein.
ISIL spokesman Abu Mohammed al-Adnani vowed the jihadists would not stop there, but would press on to the capital and the Shia shrine city of Karbala, visited by millions of pilgrims from around the world each year.
The Shia-led government in Baghdad has been left floundering by the speed of the jihadist assault. Prime Minister Nuri al-Maliki said he would seek parliament's authorisation to declare a state of emergency but MPs failed to muster a quorum for the vote yesterday.
The swift collapse of Baghdad's control comes on top of the loss of Fallujah, west of Baghdad, at the start of the year. It has been a blow for Western governments that invested lives and money in the invasion that toppled Saddam.
Washington is considering several options for offering military assistance to Baghdad, including drone strikes, a US official told AFP on condition of anonymity.
Resorting to such aircraft -- used in Afghanistan, Pakistan and Yemen in a highly controversial programme -- would mark a dramatic shift in the US engagement in Iraq, after the last American troops pulled out in late 2011.
But there is no current plan to send US troops back into Iraq, where around 4,500 American soldiers died in the bitter conflict.
Nato chief Anders Fogh Rasmussen said he saw no role in Iraq for the Western alliance in the battle against Islamists.