In northwest Baghdad, a parked car exploded outside a busy restaurant in the Shiite neighborhood of Shula, killing 13 people and wounding 37, police said.
Naseer Ali, owner of a grocery shop, said he was about 150 yards from the restaurant when the blast went off. Ali said he and others rushed to help the victims before the ambulances arrived.
Ali said he was worried the level of violence in Baghdad would return to what it was several years ago, in part because of the growing sectarian divide underlying a months-long paralysis of Iraq's government.
"The politicians are busy with their personal ambitions, and the insurgents are making use of this," said Ali, standing on the sidewalk, his shirt stained with blood.
Elsewhere in Baghdad, a parked car blew up near the home of Jamal-Din Mohammed, an adviser to Prime Minister Nouri al-Maliki, killing a civilian and wounding four people, including two guards protecting Mohammed's house.
Earlier Thursday, explosions hit two adjacent homes of Baghdad policemen in the predominantly Sunni neighborhood of Amariyah, killing two people and wounding nine, among them three children. One of the policemen was killed and the other was wounded.
A fifth attack targeted a police patrol in Baghdad, killing a policeman and wounding three officers.
In Mosul, about 225 miles northwest of Baghdad, a police major was killed when gunmen sprayed his car with bullets in a drive-by shooting, police said.
Medics at hospitals confirmed the casualties. All officials spoke on condition of anonymity.
Despite the overall drop in violence, deadly bombings are still common.
On April 19, bombs struck 10 Iraqi cities, killing 30 people and wounding more than 110. In Baghdad, 12 people were killed that day, mostly in Shiite neighborhoods.
The political impasse appears to have opened the door to violence. The unity government headed by Maliki, a Shiite, has been largely paralyzed since the withdrawal of U.S. troops from Iraq.
There is rising criticism of Maliki within the ruling coalition, over complaints that he is shutting out Iraq's two main minorities - Kurds and Sunni Muslims - in decision-making. However, his opponents appear to be falling short of a needed majority in parliament to bring him down.