Two car bombs kill at least 59 people and wound more than 140.
Monday’s bombings came as Iraqis marked the first anniversary of a Shia shrine bombing that pushed the country to the brink of civil war.
Overnight, mortar shells had crashed into Suwaib, a suburb in the south of the city, killing three civilians, the security officia said.
Speaking of Tuesday’s bombing, a security official said: “There were women and children among the victims, including 12 people from the same family killed or wounded when their nearby house collapsed.”
US soldiers joined their Iraqi counterparts in securing the scene.
The carnage came despite a massive security operation by US and Iraqi forces, and one day after a series of bombings in market areas killed at least 79 people outright and saw 165 taken to hospital.
In the Mansur district, near where Tuesday’s suicide bomber struck, traffic was funnelled on to main roads by concrete barricades and protected by Iraqi checkpoints.
Brigadier-General Abdel Karim Khalaf said that three suspects – including two whom he described as “Asians” – were being interrogated after being arrested following Monday’s blitz on the capital’s commercial centre.
“If I told you any more, it would hurt the investigation, but we are making progress,” the interior ministry operations chief told AFP.
The attacks – three car bombs in a bustling wholesale trading area and an explosive device in a popular market area – struck a terrible blow to Nuri al-Maliki’s authority as he paraded his security plan.
Television coverage of a speech the Iraqi prime minister gave on Monday calling on Iraqis to back the deployment of thousands of police and military reinforcements showed his team flinching as the sound of the explosion echoed round Baghdad.
On Tuesday, his troops were once more out in force, manning checkpoints around the city, but for many war-weary Iraqis the timing and scale of the attacks confirmed suspicions that the situation is beyond his control.