Attacks in more than a dozen cities across Iraq on Monday killed 66 people, including 40 in twin blasts in the southern city of Kut, in the bloodiest day in Iraq this year.
The surge of violence raises questions over the capabilities of Iraq's forces after its leaders agreed to open talks with the US over a military training mission to last beyond a projected year-end American withdrawal.
The attacks, in which more than 230 people were wounded, were quickly condemned by parliament speaker Osama al-Nujaifi, who blamed security leaders for unspecified "violations."
In Monday's worst attack, a roadside bomb in the centre of Kut, 160 kilometres (100 miles) south of Baghdad, at 8:00 am (0500 GMT) was followed minutes later by a nearby car bomb, medical and security officials said.
"I was on my way to my shop in the market and suddenly I felt myself being thrown to the ground," said 26-year-old Saadun Muftin, speaking from the city's Karama hospital.
"After that I found myself in the hospital with wounds all over my body."
Another shopkeeper, Mohammed Jassim, described "smoke everywhere" in the square where the blasts took place.
Dhiauddin al-Ubudi, health director for Wasit province, of which Kut is the capital, put the toll at 40 dead and 65 wounded, with both figures including women and children. Security officials cordoned off the site of the attacks in their aftermath.
The attack was the worst single incident of violence in Iraq since July 5, when twin suicide attacks killed 35 people in a town north of Baghdad.
In Saddam Hussein's hometown of Tikrit, meanwhile, three policemen were killed and at least seven others were wounded when two suicide bombers blew up their explosives-packed vests inside the city's anti-terror headquarters.
"They managed to enter wearing police uniforms and using fake IDs, passing three checkpoints," said a security official, speaking on condition of anonymity. He said among those killed in the attack were Salaheddin province's deputy anti-terror chief.
"They were trying to free Al-Qaeda fighters from the anti-terror department's jail," the official added.
In the restive province of Diyala, north of Baghdad, eight people were killed and 35 wounded in a series of attacks in provincial capital Baquba and five other cities, Diyala health department spokesman Faris al-Azzawi said.
Four of the dead were soldiers gunned down at an Iraqi army checkpoint in Baquba, according to Firas al-Dulaimi, a doctor in the city's main hospital.
Provincial government offices have been evacuated.
Two car bombs, the second of which was detonated by a suicide attacker, were also detonated in the holy Shiite city of Najaf, provincial police chief General Abdul Karim Mustafa said. A provincial health spokesman said seven people were killed and 60 wounded.
A car bomb east of Karbala, another holy city in Iraq's south, killed two and wounded nine others, provincial council chief Mohammed al-Mussawi said.
Separate explosions in the disputed northern city of Kirkuk killed one and wounded 14, while twin blasts in the western city of Ramadi left one dead and injured seven others.
A car bomb and three roadside bombs killed two people and wounded 20 in Baghdad, and bomb attacks in Taji and Balad, just north of the capital, killed one and injured 14.
Twin blasts in the northern city of Mosul also left one dead and three wounded, police said, and an explosion in the town of Iskandiriyah, south of Baghdad, injured four.
There was no immediate claim of responsibility for the attacks.
The attacks come after Iraqi leaders said on August 3 they would hold talks with the US over a security training mission to last beyond 2011, when all 47,000 American soldiers must withdraw under the terms of a 2008 bilateral security pact.
Violence in Iraq has declined from its peak in 2006 and 2007, but attacks remain common. A total of 259 Iraqis were killed in attacks in July, the second-highest figure for 2011.