At least 54 people were killed and more than 140 wounded by 12 car bombs in Shia Muslim areas in Baghdad on Monday morning.
The blasts occurred during the morning rush hour. Groups of labourers were among the targets at markets and car parks.
The BBC reports there has been a recent upsurge in sectarian killings in Iraq.
One of the bloodiest attacks over the past few weeks was a double bombing at a funeral marquee in Sadr City on 21 September, which left more than 60 people dead.
Several dozen people died in a wave of attacks on Sunday, including another explosion at a funeral.
A suicide bomber attacked a Shia Muslim mosque south of the city, causing the roof to collapse. The BBC reports more than 40 people are now known to have been killed in that incident.