A dozen car bombs and suicide blasts have targeted Shia districts around Baghdad, killing more than 65 people and injuring dozens more.
The attacks come on the tenth anniversary of the US-led invasion of Iraq that ousted Saddam Hussein.
The bombs exploded in a busy Baghdad market, near the heavily fortified Green Zone and in other districts across the capital.
A suicide bomber also attacked a police base in a Shia town south of the capital.
Sunni Islamist insurgents linked to al-Qaeda have vowed to step up attacks on Shia targets since the start of the year.
Their aim is to provoke sectarian confrontation and undermine Shia Prime Minister Nuri al-Maliki's government.
No group has claimed responsibility for the Baghdad blasts, but Islamic State of Iraq, a wing of al-Qaeda, has vowed to regain ground lost in its war with US troops.
A decade after US and British troops ousted Saddam from power, Iraq still struggles with insurgents, sectarian friction and political feuds among Shia, Sunni and Kurdish factions.
In a sign of concern over security, the cabinet today postponed local elections in two provinces, Anbar and Nineveh, for up to six months because of threats to electoral workers and violence there.
The polls will go ahead elsewhere on 20 April.