More than 30 bombs struck cities and towns across Iraq, killing at least 52 people and wounding about 250, according to the Reuters News agency.
The explosions come as final preparations for next week's Arab League summit in Baghdad are made.
The deadliest incident occurred in the southern city of Kerbala, where twin explosions killed 13 people and wounded 48 during the morning rush hour.
Blasts also struck in Baghdad, Mosul, Falluja and Ramadi. Police managed to defuse bombs in Baquba, Falluja and Mosul.
Most of the blasts targeted police checkpoints and patrols.
The Iraqi government has insisted it can maintain security in the country ahead of next week's Arab League summit.