There was no immediate claim of responsibility yesterday for any of the blasts, but Shi'ites are seen as apostates by hardline Sunni Islamists linked with al Qaeda, which has been regaining momentum.
Soldiers and security personnel are also prime targets for Sunni militants seeking to destabilise Iraq's Shi'ite-led government.
Yesterday's worst attack took place in the northern city of Mosul, when a man driving a car blew himself up outside a government bank where soldiers were waiting to collect wages, police said. Twelve people were killed.
A further 37 people died in apparently co-ordinated blasts in and around Baghdad. In the worst of those, two car bombs exploded moments apart near a busy market in the town of Nahrawan, south of the capital, killing seven.
"Al Qaeda was forced underground in 2007 and violence eased in the following years, but is now on the rise again, with around 3000 civilians killed so far this year, according to monitoring group Iraq Body Count. Insurgents have exploited growing anger among Iraq's Sunni minority, which complains it has been marginalised under the Shi'ite-led government that came to power following the US-led invasion in 2003.
A raid on a Sunni protest camp in April touched off a violent backlash by militants that continues to flare up.
Relations between Islam's two main denominations have come under further strain from the civil war in neighbouring Syria, which has drawn Sunnis and Shi'ites from Iraq and the wider region into battle.
Al Qaeda's Syrian and Iraqi affiliates merged earlier this year to form The Islamic State in Iraq and the Levant, which has claimed responsibility for attacks on both sides of the border.