The fighters seized the town of Dhuluiyah, a municipal councillor, a police colonel and witnesses told AFP by telephone.
The nearby Muatassam area has also fallen to militants, the municipal council member and witnesses said.
ISIL spokesperson Abu Mohammed al-Adnani promised the group would push on to Baghdad and Karbala, a city southwest of the capital that is one of the holiest sites for Shias, in a statement.
With militants closing in, Iraq's parliament was to meet for an emergency session Thursday to consider a request from Prime Minister Nuri al-Maliki and the president's office for it to declare a state of emergency.
Doing so requires a two-thirds vote, making it unlikely to pass the sharply divided parliament, which has produced little significant legislation in years and is often poorly attended.
US mulls air strikes
As militants sweep closer to Baghdad, UN Security Council was prompted to convene crisis talks Thursday while the US mulls air strikes on the rebels.
The UN Security Council swiftly convened a meeting to discuss the crisis in a sign of growing international alarm at the fast-moving situation.
Diplomats said the closed consultations would begin at 11:30am local time and will include a briefing by video link from the UN special representative to Iraq, Nickolay Mladenov.
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 and Pakistan 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.
State Department spokesperson Jen Psaki said the US was committed to "working with the Iraqi government and leaders across Iraq to support a unified approach against ISIL's continued aggression."
But there is no current plan to send US troops back into Iraq, where around 4,500 American soldiers died in the bitter conflict.
White House spokesperson Jay Carney said Washington "strongly condemns" the ISIL attacks and "will stand with Iraqi leaders".
And UN Secretary-General Ban Ki-moon urged the international community to unite behind Iraq, warning that "terrorism must not be allowed to succeed in undoing the path toward democracy in Iraq."
COMMENTS (14)
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@ali:
forget secret alliances what about the very real one between all sunni countrys and USA.
....and why did the US invade Iraq ?
This is a frightening development. We must support the Iraqis in bringing down the terrorist group ISIL.
Who would have thought that some day Iraqis would be reminiscing the 'good ol' days of Saddam'
@unbelievable: NONE
Is there any Islamic country where Sunni and Shia get along?
Americans can give best equipment, training and uniforms but cannot give will to fight. Chicken remain a chicken whatever attire it wears.
Back to square one. Iraq calling for American help to bomb the Islamists and Pakistan calling American help to drone the TTP hide outs. Blame America for all your ills and fall back on their feet for help.
@ali:
What you wrote did not make sense next time try writing in english I know thats very hard for you.
All sunni countrys around the world are friends with USA what does that tell you.
ET why do you always print pro terrorist comments but never pro peace like mine.
Iran must get involved to protect Iraq against Sunni extremists.
So us did not protected Sunnis in syria against shia aggression and in Iraq iranian regime will be protected by us we all know now of the secret alliance btw iranian regime and us and israel
Hay ET !!! What does it mean Militants ? Whom you are saying Militants ??
There are no winners in any war , there are mere survivors .