Rush hour bombs mostly targeting Shiite areas of Baghdad killed 25 people on Tuesday in the first major wave of attacks in the capital since a general election last month.
The apparently coordinated blasts struck as Iraq's Shiite majority marked the birth of a venerated figure in their faith, and came as officials tallied votes from the April 30 election amid a protracted surge in bloodshed that has killed more than 3,300 people this year.
The government has blamed external factors, such as the civil war raging in neighbouring Syria, for the escalating unrest.
But analysts and diplomats say the Shiite-led authorities have failed to do enough to reach out to the disaffected Sunni Arab minority and undercut support for militancy.
At least nine car bombs went off through the morning, when traffic gridlocks the streets.
Smoke could be seen rising above several areas of the capital, and AFP journalists reported several shopfronts badly damaged and nearby cars reduced to mangled wrecks of metal.
At least 80 people were wounded, overall.
In Karrada, where three people died, the owner of a garage said the blast was caused by a militant posing as a customer who left his car, asking for the brakes to be fixed.
"He said he would leave the car and go looking for spare parts, and then he left," said the 54-year-old who identified himself as Abu Nuri.
"Only one of my employees was in the shop when a huge explosion went off. He fell down, and smoke was everywhere. Many people were crying, and others were running away."
Abu Nuri railed against the authorities and security forces, telling AFP: "The state has failed, it has completely failed.
"Attacks target only innocent people, and those heroic officials are completely protected in the Green Zone," he said, referring to the heavily-fortified Baghdad district, which is home to parliament and the US and British embassies.
Mostly Shiites targeted
Two car bombs also exploded near a traffic police headquarters in the eastern Baladiyat neighbourhood, and blasts also hit Sadr City, Urr, Jamila, and Maamal, all of which are Shiite-majority.
Another vehicle rigged with explosives was detonated in the mostly-Sunni area of Arab Jubour, killing three, while a roadside bomb went off near a police patrol in southeast Baghdad, killing one.
Elsewhere, two people, including a young boy, were killed in a rocket attack just north of the capital, while two others died in a car bomb in the town of Balad and a police officer was killed in the main northern city of Mosul.
No group immediately claimed responsibility for the attacks.
But Sunni militant groups have in the past set off coordinated bombings in the capital and often target the country's Shiite majority, whom they regard as apostates.
The attacks came as Shiite Muslims marked the birthday of Imam Ali, the cousin and son-in-law of the Prophet Mohammed, and a key figure in Shiite Islam.
Interior ministry spokesman Brigadier General Saad Maan, who has criticised the media in the past for exaggerating the level of unrest, played down the city-wide violence, saying in a statement that only one civilian had been confirmed wounded.
Iraq is suffering its worst violence since the Sunni-Shiite sectarian conflict that killed tens of thousands of people in 2006-2007.
Security officials had expressed concern that militants could seek to exploit the vote count and what is expected to be a prolonged period of coalition talks afterwards to launch attacks aimed at further fraying already fragile ties between Iraq's communities.
The authorities have trumpeted security operations targeting militants in the north and west, insisting they are making progress against a variety of militant groups, including the jihadist Islamic State of Iraq and the Levant.
But anti-government fighters have continued to hold on to Fallujah, a city a short drive from Baghdad, as well as other pockets of territory in the west.