Bombers targeted two markets in Baghdad province on Thursday, killing at least 19 people, as two more died in other attacks, officials said.
Four bombs in Saba al-Bur north of the capital killed at least 12 people, while another in the predominantly Sunni neighbourhood of Dura in south Baghdad killed seven.
At least 50 people were wounded, the officials said.
Militants in Iraq often bomb areas where crowds of people gather, and have struck this year at markets, football pitches, cafes, mosques and at weddings and funerals.
Also on Thursday, a magnetic "sticky bomb" on a car killed a policeman and wounded two civilians in the northern city of Mosul.
Another similar device killed an employee of a local television station and wounded a second in Baquba, also north of Baghdad.
Iraq is experiencing its worst violence since 2008, when it was just emerging from a brutal sectarian conflict.
There are persistent fears of a return to the all-out Sunni-Shiite sectarian violence that peaked in 2006-2007 and killed tens of thousands of people.
The latest violence takes the death toll to almost 700 people this month and more than 4,500 this year, according to AFP figures based on security and medical sources.
Diplomats and analysts say the Shiite-led government's failure to address the grievances of the Sunni Arab minority, who complain of political exclusion and security force abuses, has driven the spike in violence.
The civil war in neighbouring Syria has also fuelled sectarian tensions in Iraq.