In the latest in a series of attacks that killed 99 people, three bombs hit the southern Shiite port city of Basra in the evening. At least one exploded in a marketplace, killing at least 15, hospital and police officials said.
The violence began in the capital where at least 10 people were killed in what appeared to be coordinated attacks against police and army checkpoints across Baghdad. Both Shiites and Sunnis were targeted in attacks around the country.
The most deadly incident was an afternoon bombing in the Shiite city of Hillah, the capital of Babil province 60 miles (95 kilometers) south of Baghdad. A suicide bomber with explosives strapped to his belt blew himself up among a crowd trying to help victims of two car bombs that went off earlier outside a textile factory, said Babil provincial police spokesman Maj. Muthana Khalid.
At least 45 were killed and 140 wounded in the triple blasts, Khalid and al-Hillah hospital director Zuhair al Khafaji said. Witnesses said they saw blood pooled and pieces of flesh on the ground outside the factory.
"Terrified people were running in different directions," said Jassim Znad Abid, a taxi driver who lives in Hillah. "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 laying on the ground."
Khalid said the two car bombs parked outside the factory about 25 yards (meters) apart exploded first as workers were leaving the factory around 1:30 p.m. They were believed to be detonated by remote control.
Then as rescuers and workers were trying to help the injured, the suicide attacker struck.
Babil provincial Gov. Salman Nassir al-Zargawi ordered flags lowered to half-staff and a three-day mourning period. In an interview with Iraqi state TV, al-Zargawi said he was informed Sunday that the factory was under threat, but cited too many security gaps across Babil to protect all sites he feared could be targeted.
"There are many fragile places especially in the north of Babil... and there are a lot of security gaps there," al-Zargawi said. "So we are facing a daily challenge in Babil."
The day's violence began in Baghdad with the checkpoint attacks. Most of the incidents were drive-by shootings in which assailants wearing uniforms of city government employed cleaners used weapons fixed with silencers to spray checkpoints and patrols with bullets.
Maj. Gen. Qassim al-Moussawi, spokesman for Baghdad's security operations center, said Iraqi security forces arrested one suspect and seized a pistol with a silencer.
The violence delivered a chilling reminder that insurgents are still able to stage large scale operations despite security gains by Iraqi and U.S. forces over past years.
There was no immediate claim of responsibility. But al-Moussawi blamed al-Qaida in Iraq for the Baghdad attacks, saying the terror group is attempting to exploit Iraq's political instability.
"Al-Qaida is trying to ... use some gaps created by some political problems," the Iraqi security spokesman told Arabiya TV. "There are well-known agendas for the terrorist groups operating in Iraq. Some of these groups are supported regionally and internationally with the aim of influencing the political and democratic process inside Iraq."
U.S. Maj. Gen. Stephen Lanza, the top military spokesman in Iraq, said the attacks show "there is a threat out there that we have to be concerned about, and the threat is still capable."
Violence in Iraq has fallen dramatically since the height of the insurgency in 2006 and 2007. But the political vacuum in the wake of the inconclusive election has raised the risk that sectarian violence will pick up again.
Former Prime Minister Ayad Allawi's Iraqiya coalition, a secular group heavily backed by the Sunni Arab minority, edged out Prime Minister Nouri al-Maliki's religious Shiite bloc by two seats in the parliamentary election but neither won an outright majority, forcing them to seek partners to form a ruling coalition.
Last week al-Maliki's State of Law coalition formed an alliance with the religious Shiite Iraqi National Alliance believed to have strong backing from Iran, a deal that put them four seats short of a majority in parliament and did not include Allawi. The pact could lead to four years of another Shiite-dominated government much like the current one.
Sunni anger at Shiite domination of successive governments was a key reason behind the insurgency and if Allawi is perceived as not getting his fair share of power, that could in turn outrage the Sunnis who supported him.
In other attacks Monday the small town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, was hit by a pair of bombs -- one in a parked car and the other planted along a road -- that killed 11 passers-by and wounded dozens, an Iraqi police official and a hospital worker in the nearby city of Kut said.
In Tarmiyah, 30 miles (50 kilometers) north of Baghdad, city Mayor Mohammed Jassim was injured when bombs in parked cars targeted his convoy. In all, five people were killed and 18 injured in the attack, said a city police official.
At least six people were killed west of Baghdad in the city of Abu Ghraib by three different bombings , Iraqi officials said.
Seven more were killed in four separate attacks stretching from the northern city of Mosul to the Shiite city of Musayyib south of Baghdad.