Aftermath of one of the bomb attacks in Baghdad
More than 100 people have died and 350 been wounded in a series of shootings and suicide bombings in Iraq - the worst day of violence there this year.
The central city of Hilla saw the deadliest attack, when staff at a textiles factory were hit by three bomb attacks, killing at least 45 people.
The violence began with a series of drive-by shootings targeting police and army officers in the capital Baghdad.
Iraq remains in political stalemate after inconclusive elections in March.
Both Iraqi and US officials have warned that the political situation could be exploited by al-Qaeda.
Two car bombs exploded in quick succession at the entrance to the textile factory in Hilla, just as workers boarded buses to go home in the middle of the day.
Later, as bystanders and emergency services rushed in to help the wounded, a suicide bomber detonated explosives causing a third explosion.
At least 45 people were killed and more than 140 were wounded.
"Terrified people were running in different directions," said witness Jassim Znad Abid.
"I saw dead people, some burned and crying, wounded people on the ground that was covered with pools of blood. Dozens of wounded people asking for help were lying on the ground."
At dawn on Monday, gunmen with silencers fitted to their weapons drove up to checkpoints across Baghdad, killing at least seven police and army officers.
In other violence:
A double suicide bombing in a crowded market in the small town of Suwayra, south of Baghdad, killed at least 11 people and wounded more than 40 The southern oil hub of Basra was struck by three car bomb attacks, killing at least 20 people and wounding dozens more Two bombs went off in the mainly Sunni town of Falluja, killing at least four people, including a police officer and his wife There were also attacks in Iskandiriya, south Baghdad, and in Mosul, north of the capital.
Monday's violence has been blamed on al-Qaeda in Iraq, and it looks like a strong signal that they are still a force to be reckoned with, says the BBC's Gabriel Gatehouse in Baghdad.
Only last month, US and Iraqi officials had claimed a major victory after killing the militant organisation's two highest-ranking members.
Official figures show that 328 people were killed in Iraq in April, slightly fewer than a year ago.