Insurgents have launched fierce attacks that killed about 100 people in five Iraqi cities, wreaking havoc just days from the handover of power.
Hospitals struggled to cope with casualties
The worst attacks were in the city of Mosul, where at least 62 people died and 220 were hurt in a series of car bombings, the US military said.
More than 40 people died in Baquba, Ramadi, Falluja and Baghdad, in what appeared to be co-ordinated attacks.
Iraq's interim prime minister, Iyad Allawi, vowed to crush the insurgents.
Three US soldiers were killed in Thursday's raids in the Sunni Muslim heartland, which began at dawn when insurgents seized police stations in Baquba.
Brigadier General Mark Kimmitt, deputy director of operations for the US army in Iraq, said security was restored by noon (0800 GMT).
TOLL OF CASUALTIES
Mosul: 62 dead and 220 hurt
Ramadi and Falluja: 20 dead and 76 wounded
Baquba: 13 dead and 15 wounded
Baghdad: 8 dead and 13 wounded
Sources: US military and Iraqi health ministry
"With the exception of what we are seeing in Baquba, most seem to be under control right now," he said.
Mehdi Army truce
Late on Thursday, the Shia militia loyal to radical cleric Moqtada al-Sadr declared a unilateral truce in the Sadr City slum quarter of Baghdad - the final area where it was still opposing US-led coalition forces.
"For the sake of the public interest and considering the sensitive situation the oppressed Iraqi people are under, the Central Mehdi Army Command announces a halt to military operations within Sadr City," the militia said in a statement.
It was unclear which group, if any, co-ordinated Thursday's attacks.
Interim Prime Minister Iyad Allawi said the authorities had expected such an escalation in the run-up to the coalition's 30 June handover power to an Iraqi interim government.
"We are going to defeat them and we are going to crush them," he vowed.
US Secretary of State Colin Powell told the BBC: "I think we underestimated the nature of the insurgency that we might face during this period.
"The insurgency that we're looking at now has become a serious problem for us, but it's a problem that we will deal with."
A statement on a Saudi website on behalf of Jordanian-born Islamist, Abu Musab al-Zarqawi, claimed his group carried out the Baquba attack.
Arabic TV channel al-Jazeera showed insurgents in Baquba claiming to be Zarqawi followers.
MONTH OF VIOLENCE
22 June: US says it kills 20 militants in Falluja air strike
21 June: Four US soldiers die in Ramadi ambush
17 June: 41 die in car bomb attacks in Baghdad
16 June: Iraqi oil fields security chief killed in Kirkuk
14 June: 12 die in Baghdad car bomb
13 June: Education ministry official killed in Baghdad
12 June: Interim deputy foreign minister Bassam Qubba killed in Baghdad
8 June: Car bombs kill 15 in Mosul and Baquba
But Mr Allawi said he believed a group linked to Zarqawi was behind the Mosul bombings and that the Ramadi and Baquba raids were by Saddam Hussein loyalists.
The BBC's Middle East analyst, Roger Hardy, says it is not clear that there is a single command centre organising the violence and that Zarqawi's group may be one among many.
A US patrol was ambushed in Baquba. Military spokesman Major Neal O'Brien said: "The patrol returned fire, killing two insurgents.
"There also have been reports of indiscriminate fire, landing in populated areas. They're firing mortars indiscriminately."
- there were at least four bombings
- car bombs went off in the al-Wakhas district and on the Wadi Hajar police station in the south of the city
- the Iraqi Police Academy, another police station and the al-Jumhuri hospital were also attacked, said police and doctors
- insurgents fought running
battles with US troops and Iraqi police
In Baquba, 55km (35 miles) north-east of Baghdad:
- witnesses said masked men in black took control of the main road and attacked a police station with assault rifles and rocket-propelled grenades
- two US soldiers died in the Baquba fighting and seven were wounded, the US army said
In Ramadi, 100km west of the capital:
- black-clad insurgents fired rocket-propelled grenades at two police stations, police said
- seven people were killed and 13 were wounded in the attack, hospital officials said
two other groups of insurgents attacked a second police station and a government building
- the US military said a Cobra helicopter was shot down but there were no casualties
- US warplanes and helicopter gunships flew low over the city in response to gunfire and rocket-propelled grenades
- four members of Iraq's national guard died and two people were hurt in a car bomb blast