Early morning attacks on mostly Shia targets across Iraq have killed at least 60 people and wounded dozens more.
It was one of the bloodiest days of violence since US troops pulled out in mid-December.
The violence breaks weeks of relative calm as Shia Prime Minister Nouri al-Maliki and Sunni leaders have sought to resolve a political crisis that followed the US withdrawal.
At least 32 people were killed in blasts in Baghdad where ten bombs exploded in Shia neighbourhoods during rush hour.
Other attacks in the capital targeted police patrols, commuters and crowds gathered in shopping areas.
More than a dozen blasts and attacks hit other cities across Iraq from Mosul in the north to Hilla, south of Baghdad, many of them targeting police.
Iraqi officials had predicted such groups would try to stir sectarian tension with attacks after US forces went home.
One car bomb in the capital killed at least nine people and wounded 27 in the upmarket Karrada neighbourhood, hurling shrapnel into the next street and blowing out glass from nearby buildings.
At least two other blasts hit Karrada, including another car bomb attack that killed one person, police said.
Witnesses saw at least four wrecked cars full of shrapnel and bloodied seats near a popular ice-cream shop.
In at least three Shia neighbourhoods in Baghdad, nine policemen were killed, and in the capital's northwestern Kadhimiya district, a car bomb killed six people when it struck a street lined with restaurants.
Another car bomb targeting a police patrol in the mixed Mansour neighbourhood killed two people.
Twin roadside bombs killed two people and wounded nine in the southern Doura neighbourhood, police said.
In the biggest attack outside the capital, a car bomb killed seven people and wounded 33 in the town of Balad, north of Baghdad.
