The death toll in a series of coordinated bombings in eastern Baghdad rose to 200 on Friday, prompting the authorities to impose an indefinite curfew.
A further 250 people were wounded when four car bombs in quick succession struck 55th Square, al-Sadrain Square, the popular Hai market and Mudhafar Square in Sadr City on Thursday.
Some people warned the latest carnage was likely to inflame sectarian passions and push the country closed to a full-scale civil war.
Sadr City in eastern Baghdad is a stronghold of the followers of radical Shia cleric Muqtada al-Sadr.
The revered cleric's militia Mahdi Army is often accused of getting involved in the sectarian violence, in which thousands of people have been kidnapped and tortured and their bodies dumped.
Angry residents and armed militiamen flooded the streets on Thursday to protest the bloody attacks, denouncing Sunni militants.