"Despite strong strikes that broke al-Qaeda, there are some cells still working, attempting to prove their existence and their influence," Major General Qassim al-Moussawi, Baghdad's security spokesman, said.
In the bloodiest incident on Monday, two suicide car bombers drove into the entrance of a textile factory as workers were ending a shift in the town of Hilla, south of Baghdad, a regional office of the national media centre said.
A third bomb exploded as police and medics rushed to the scene, causing additional casualties. At least 36 people were killed and more than 140 others wounded.
"This looks like a major campaign by the terrorists, not just in Hilla," Salman al-Zarqani, the governor of Babil province, said.
In an interview with Iraqi state TV, al-Zarqani said he was informed on Sunday that the factory was under threat, but there were too many vulnerable sites to provide security at all of them.
"There are many fragile places especially in the north of Babil," he said. "So we are facing a daily challenge in Babil."
Al Jazeera's Mike Hanna, reporting from Baghdad, said that security forces were believed to have been expecting a reaction to the arrests of high-profile members of al-Qaeda in Iraq.
"Certainly, authorities were predicting a backlash against that, we had seen a number of attacks recently, but this is the most serious in terms, not only of the death toll, but of the sense of co-ordination," he said.
"It would be a very strong answer, if indeed it is an al-Qaeda group [behind Monday's strikes], that despite the fact that their leadership is gone, they are still capable of carrying out this type of attack."
Abu Ayub al-Masri, the leader of al-Qaeda in Iraq, and Abu Omar al-Baghdadi, the purported leader of al-Qaeda's local affiliate, the Islamic State of Iraq, were killed in a raid on their safehouselast month.
The US has pledged to withdraw all its combat troops from Iraq by the end of August this year.
Raed Jarrar, an Iraqi political analyst based in Washington, said that if Monday's attacks were actually carried out by al-Qaeda, it could be an act aimed at making the US prolong its stay in the country.
"Al-Qaeda would love to see a longer US occupation," he told Al Jazeera.
"The US occupation of Iraq has been one of the best tools that al-Qaeda has to kill more Americans, to drain the US treasure and money and to recruit more extremists."
|Today's attacks undermine US confidence in Iraqi security performance [Reuters]
But Jarrar said ordinary Iraqis wanted the US to stick to its August 31 deadline.
"I don't think Iraqis view US military presence as protecting them or helping to stabilise the country. Prolonging the US occupation would add yet another layer of complexity and problems to the already tense situation."
More than a dozen of the attacks on Monday occurred in Baghdad, executed within hours of each other, with assailants using silenced and automatic weapons, roadside bombs and cars rigged with explosives.
The attacks came just two days after reports that the Iraqi defence ministry was considering building a "security fence"around the capital as a way of curbing violence and controlling the movements of anti-government fighters.
Bombings also took place in the southern city of Basra, Suweira in Wast province, Mosul, Fallujah and Tamiya, north of Baghdad.
Security forces hit
Security forces were the apparent target of much of the violence, with patrols and checkpoints manned by local and federal police, as well as the Iraqi national army, all being hit.
"The terrorist gangs perpetrated new assaults today on our people and armed forces," Adel Abdul-Mahdi, one of Iraq's vice-presidents, said.
He stressed the importance of moving quickly to form a government, as the major political blocs continue their attempts to secure a coalition more than two months after the March 7 polls.
"We call on all political blocs to work seriously for the benefit of the country and ... start to form a national partnership government including all political parties without marginalising any one."
The Iraqiya bloc, which won the most seats in the parliamentary election, last week warned that a dealbetween the State of Law coalition and the Iraqi National Alliance, another Shia party, could bring a return to sectarian violence.
'Violence and chaos'
The alliance threatens to marginalise the secular Iraqiya bloc, which is led by former Shia prime minister Iyad Allawi and largely backed by Sunnis, as it gives State of Law and its allies the power to dominate parliament.
The United States said that the perpetrators of Monday's violence were making a final attempt to create chaos, exploiting the political situation in the country.
"We have always known and planned for, in the period of governmental formation, that those whose violent grip slowly diminished over several years ... would make one last charge at trying to foment violence and chaos," Robert Gibbs, the White House spokesman, said.
"The vice-president [Joe Biden] has been working on the political situation there, and we continue to believe we're making progress."
Violence across Iraq has dropped significantly since 2006 and 2007, when the country's sectarian conflict was at its height. But attacks have been on the rise in recent months, particular in Baghdad.
Monday's violence came after figures showed the number of Iraqis killed in violence in April fell slightly month-on-month but was almost unchanged from 12 months ago. At least 328 people died as a result of attacks last month.