Bombs left inside busy markets in mainly Sunni Muslim districts of Baghdad killed at least 23 people on Thursday, police said.
The deadliest attack took place in Saba'a al-Bour on the capital's northern outskirts, where three bombs killed at least 15 people.
In the Doura district of southern Baghdad, a bomb exploded in another market, killing at least eight people, police said.
Relations between Iraq's communities have come under acute strain from the civil war in neighbouring Syria, where mainly Sunni rebels are fighting to overthrow a leader backed by Shi'ite Iran.
Nearly 6,000 people have been killed in violence so far this year, according to monitoring group Iraq Body Count, reversing a declining trend in violence after a peak in 2006-07.
Unidentified gunmen raided the house of a prominent member of a government-backed Sunni "Sahwa" militia, shooting him and his four sons dead early Thursday in Latifiya, 40 km (25 miles) south of Baghdad, police said.