Iraqi authorities say two people - including at least one child - were killed in a bombing at a playground as children were celebrating the Islamic festival of Eid al-Fitr.
Officials say at least 17 people, including children, were wounded Friday when the bomb hidden in a cart of toys detonated in the northern town of Tuz Khormato.
In other violence in Iraq, officials say a car bomb blast in Baghdad killed four people, including two policemen, and wounded 15 others.
Separately, the U.S. military says it is investigating a coalition raid Thursday that killed 15 civilians northwest of Baghdad.
The military says the operation targeted senior al-Qaida leaders in the Lake Thar Thar region. The military says ground and air assault troops acted on intelligence reports that the terrorist leaders were meeting in the area.
It says supporting aircraft responded after coalition forces were hit by small arms fire.
The military says the civilians killed were six women and nine children. U.S. military spokesman Major Brad Leighton said coalition forces regret the civilian deaths. He said the militants deliberately placed innocent Iraqi women and children in danger by their actions and presence.
A U.N. report issued Thursday says the ongoing violence within Iraq has displaced about 2.2 million people and caused a similar number of refugees to flee the country.
Some information for this report was provided by AP and Reuters.