In the deadliest attack, two mortar rounds fell on a soccer field in the east Baghdad suburb of Sadr City, a stronghold of Shiite militias, and a teeming slum that is home to more than two million people.
The shelling killed eight people and wounded 15, and appeared to be the latest in a series of tit-for-tat attacks that alternate between the battered city's Sunni and Shiite neighbourhoods.
The US military also reported the deaths of two servicemen, a soldier and a marine, in separate incidents.
The day began with a mortar attack near the health ministry, controlled by followers of radical Shiite cleric Moqtada al-Sadr, in which three people were killed and five wounded, a security source said.
At about the same time, a car bomb exploded near the Nida mosque in the northern Sunni stronghold of Adhamiyah, killing one person.
Another mortar attack in downtown Jumhuriyah Street killed one person and wounded eight.
Not long afterwards, a pair of mortars crashed on Kadhimiyah neighbourhood, another Shiite stronghold and home to two holy shrines, killing two people and wounding eight.
Duelling mortar salvos between rival neighbourhoods have become a common feature of the capital's instability.
In Baghdad's southwest Al- Amil neighbourhood, three civilians were killed and another three wounded in a car bomb attack, while a member of the National Police was killed in a suicide car bombing against a southern checkpoint.
South of the city, in the rural area known as the "triangle of death", a car bomb exploded in Mahmudiyah, killing six people and wounding another 26, said security sources.
In nearby Iskandriyah, another bomb exploded in a residential area killing a man and his 13-year-old son.
Flashpoint east
In the flashpoint eastern region of Diyala, which was also under curfew along with Baghdad and Salaheddin provinces, at least 17 people were killed, including four in a single car bomb attack, police said.
In a series of shootings across the province carried out by unknown gunmen, eight people were killed, including four in Baquba.
And five Iraqis were killed when clashes broke out between two Sunni Arab tribes, al -Azah and al- Rabiya, in the village of Dhida near Muqdadiyah, police said.
The fighting began after an ex-army general from one tribe was killed allegedly by members of the other tribe, police said.
Two police lieutenants were also killed in Saddam's northern hometown of Tikrit, while hundreds of his supporters demonstrated in Salaheddin against the ousted dictator's death sentence.
On Wednesday the US military announced the deaths of two of its servicemen, including a marine killed from wounds suffered in enemy action in the Sunni Arab province of al- Anbar.
The military also announced 14 members of al- Qaeda were killed in two separate raids in Iraq, including 10 in an operation that freed a kidnapped Iraqi policeman found chained to the floor.
And a military raid in the Kirkuk area netted seven men involved in bringing in foreign fighters.