Children, shoppers and men looking for a day's work were among the dead in attacks in Baghdad, Ramadi and Baqouba, cities that saw some of the most intense fighting of Iraq's long war but have since experienced sharp drops in violence. American combat troops completed a pullout from urban areas on June 30, and Iraqi forces now take the lead in securing the cities.
Meanwhile a U.S. military spokesman said American soldiers had killed two people who attempted to throw grenades at a convoy west of Baghdad.
In addition, Lt. Col. Philip Smith said one civilian was killed and four were wounded during the attack Tuesday on the American convoy in Abu Ghraib.
An Iraqi police official gave a conflicting account of casualties. He said four civilians - a boy and three bus drivers - were killed when U.S. forces opened fire on the attackers near a bus station.
The official spoke on condition of anonymity because he was not authorized to talk to media.
The violence came as Iraqi Prime Minister Nouri al-Maliki travelled to Washington for a meeting Wednesday with President Obama, who plans to withdraw all American soldiers from Iraq by the end of 2011 and is shifting military resources to the war in Afghanistan. There was no indication that insurgents timed the attacks to coincide with the U.S. meeting, though they have in the past carried out operations around election days and other politically significant dates.
One of al-Maliki's goals is to convince U.S. investors that oil-rich Iraq is an attractive place to do business. However, continuing attacks, even at a relatively low pace, as well as American concerns that reconciliation among Iraq's factions is not moving fast enough, could hurt the prime minister's efforts.
With six months left before Iraq's next general election, Iraq's main Shiite, Sunni and Kurdish groups remain divided over issues, including how to share the country's vast oil wealth, the authority of the central government and political power-sharing.
Tuesday's violence began just after 5 a.m., when two bombs exploded a few seconds apart near a group of day laborers in the Shiite district of Sadr City in northeast Baghdad, which was often targeted at the height of sectarian bloodletting between Sunnis and Shiites in 2006 and 2007.
Police said one bomb was hidden in a food stall and the other was concealed in a trash pile, and that four people died and 31 were injured.
Ahmed Ali was working in a nearby bakery when the explosions occurred.
"After a few seconds, dust and smoke reached the bakery. We stayed inside because we feared other explosions might occur," Ali said. "After about five minutes, we went out to see what happened. We saw the bodies covered with blood and some food containers and construction tools scattered here and there."
At around 11:30 a.m., a roadside bomb exploded near a market in Sadr City, killing four people and wounding at least 21, police and hospital officials said on condition of anonymity because they were not authorized to speak to the media. The dead included a baby girl and a 10-year-old girl.
In the Dora district of south Baghdad, two people died and six were wounded when a car bomb exploded near a wholesale produce market. And in Ramadi, 70 miles west of Baghdad, a suicide car bomber targeted a restaurant and killed a doctor and injured 19 other people, including several children, said police Maj. Gen. Tareq Youssef.
Ramadi is the capital of Anbar province, a former Sunni insurgent stronghold. Police in the province on Tuesday declared a two-day ban on the use of vehicles and motorcycles as they searched for suspects in a recent spate of bombings in Ramadi and nearby Fallujah.
Also, a woman and her child were killed by a bomb hidden in trash in Baqouba, northeast of Baghdad, said police Col. Ghalib al-Kharki.
At around 7:45 p.m., bombs killed five civilians and wounded 29 in an open-air market in Husseiniya, just northeast of Baghdad, police and medical officials said. Two bombs were hidden in trash about 50 metres apart and exploded within a few seconds of each other.