A car bomb has killed at least 24 people in a northern Iraqi city, on the day that Iraqi forces officially assumed control of security in Baghdad and other urban areas.
At least 25 other people were wounded when the car bomb exploded in a market in Kirkuk. Further details were not immediately available.
The oil-rich Kirkuk region is at the center of a power struggle between ethnic and religious groups including Kurds, Arabs, Turkmen, Muslims and Christians.
Earlier Tuesday, Prime Minister Nouri al-Maliki reviewed members of the Iraqi military as a band played, and he called the day a "great victory."
The Iraqi government had declared Tuesday a "Day of National Sovereignty" to mark the withdrawal of U.S. combat troops from urban areas.
While some Iraqis are joyous at seeing U.S. combat troops leave, others are nervous about the change in security and fear an increase in militant attacks.
The withdrawal is part of U.S.-Iraq security deal that sets a timeline for the withdrawal of all U.S. forces by the end of 2011. For the time being, tens of thousands of U.S. troops will remain in the country to train and advise Iraqi forces, and to conduct combat duties outside cities.