Dozens of people have been killed and many more wounded in a series of blasts in Baghdad.
At least 63 people died and 176 people were wounded in 12 bombings across the Iraqi capital on Thursday morning, health ministry sources told Al Jazeera.
The wave of bombings come amid renewed fears of sectarian strife following the withdrawal of US troops and a deepening political crisis over an arrest warrant issued for Tariq al-Hashimi, the country's vice president and most senior Sunni politician.
The attacks largely coincided with the morning rush hour, and security forces cordoned off bomb sites, AFP news agency correspondents and officials said.
Authorities believe the attacks were well co-ordinated, Al Jazeera's Omar al-Saleh said, reporting from Baghdad.
"We don't know who carried out the attacks, the Iraqi security officials did not identify any suspects yet," Saleh said, adding: "This I think is a major setback to the security forces on the ground who have a large presence in the capital. You have checkpoints, you have roadsblocks, and you have both the military and the Iraqi police guarding different areas, yet these attacks do occur."
Iraqi officials said the bombs struck in the Allawi, Bab al-Muatham and Karrada districts of central Baghdad, the Adhamiyah, Shuala and Shaab neighbourhoods in the north, Jadriyah in the east, Ghazaliyah in the west and al-Amil and Dura in the south.
The largest explosion took place near the Rahbaat (Sisters) hospital and the Integrity and Transparency Directorate in Karrada district, sources told Al Jazeera.
The blast caused great material damage and the bodies of those killed were laid out in the streets, eyewitnesses said.
"I saw all the windows were blown out and glass scattered everywhere. The children were scared and crying," said Raghad Khalid, a teacher at a kindergarten near the Karrada blast.
"Some parts of the car bomb are inside our building."
Smoke hung over the blast site in Karrada as ambulances rushed in to ferry the wounded to hospital.
Tensions between Iraq's Shia and Sunni communities have been heightened in recent days after Baghdad officials issued an arrest warrant for Hashimi over allegations that he ordered the killings of opponents.
Hashimi denies the charges and says they are politically motivated. Some Sunnis say Nouri al-Maliki, Iraq's prime minister, is seeking to consolidate Shia control of the country following the departure last week of the remaining US troops stationed in the country.
"The fears of the people became reality," our correspondent in Baghdad said.
"I think the people are really scared and I think the politicians do know that their differences will be translated into attacks like these on the streets of Baghdad.
"From the official point of view, no one has come out yet saying there is a direct link, but among the general population they do have a fear and a genuine belief that attacks like this are a direct result of the differences between politicians," he added.
Violence in Iraq has ebbed since the height of sectarian fighting in 2006-2007 when suicide bombers and hit-squads targeted Sunni and Shia communities in attacks that killed thousands and pushed the country to the edge of civil war.