Al-Qaeda-linked militants held control of much of the Iraqi city of Fallujah and other nearby towns, fighting off efforts by troops with air support to dislodge them, according to a witness.
Al-Qaeda fighters from the Islamic State of Iraq and the Levant (ISIL) have seized military equipment provided by the US marines to Fallujah police, whose headquarters have been taken over, Uthman Mohamed, a local reporter in the city in Iraq's western Anbar province, said.
There's no sign of government forces inside Fallujah, and most of the fighting is occurring on a highway that links the city to Baghdad, he said.
A senior Iraqi military commander said yesterday that it would take a few days to fully dislodge the fighters from two key western cities.
Lieutenant General Rasheed Fleih, who leads the Anbar military command, told state television that he expected "two to three days" were needed to push the militants out of Fallujah and parts of Ramadi.
Fleih added that pro-government Sunni tribes were leading the operations while the army was offering only aerial cover and logistics on the ground.
"The quiet and safe life that is sought by the Anbaris will not be completely restored before a few hours or two to three days, God willing," Fleih said.
Residents say it had been quiet since Saturday night in Fallujah, where militants still control the centre of the city. Sporadic clashes took place yesterday in and around Ramadi. The residents spoke on condition of anonymity for their safety.
On Friday, hundreds of gunmen, some bearing the black flags often flown by jihadists, gathered at outdoor weekly Muslim prayers in Fallujah, where one militant announced that "Fallujah is an Islamic state."
Fighting began in the Ramadi area on Monday - when security forces broke up the country's main Sunni Arab anti-government protest camp - and then spread to Fallujah.
Security forces withdrew from areas of both cities, which cleared the way for militants to move in.
More than 160 people have been killed in fighting between ISIL, security forces and tribesmen in just two days.
ISIL's "strength and territorial control and influence has been expanding in Anbar for some time," said Charles Lister, a visiting fellow at the Brookings Doha Centre.
Its "objectives lie far beyond Iraq, but transnational objectives of establishing an Islamic state across the Levant can only be realised once mini-states of territorial control are realised.
"In the Iraqi context, Anbar and also Nineveh (province) are of crucial importance as a result of their direct links into eastern Syria," where ISIL is also a major player.
Defence Ministry spokesman Mohammed al-Askari also highlighted the Syrian connection.
Aerial photographs and other information pointed to "the arrival of weapons and advanced equipment from Syria to the desert of western Anbar and the border of Nineveh province," encouraging militants to rebuild once-eliminated camps, Askari said.
Security forces have targeted militant camps in recent operations in western Iraq.
John Drake, a security specialist with risk management firm AKE Group, said the situation in Anbar "is comparable to the bad days at the height of the insurgency."
But while it may add to ISIL's credibility, attempting to hold territory poses risks.
"It will give more credibility to the group, but in the longer term, it will have to tread very warily if it is to avoid incurring the wrath of the local population again," Drake said, referring to disgust with militants' brutality that led tribal fighters to turn against them.
"ISIL showed that it can strike fast and hard, exploiting the gap as Iraqi army forces withdrew from urban areas to overrun police stations," said Michael Knights, a fellow at the Washington Institute for Near East Policy.
But Knights sounded this warning: "If the Iraqi government uses this moment to re-engage the tribal awakening, al-Qaeda could be dealt a severe reverse.
"If the government sidelines the Sunni tribes and continues with a brute force approach, al-Qaeda may gain significantly in strength."