Iraqi officials say a suicide car bomber killed at least six people and wounded 34 in Baghdad.
The bomber set off his explosives near a police station in the Shi'ite neighborhood of Sadr City.
Earlier Wednesday, the U.S. military said 3,700 more American troops had arrived in Baghdad to help Iraqi security forces clear, control and retain key areas to reduce violence.
This is the fourth additional combat unit deployed in Baghdad as part of plans to add 28,000 troops there for a security crackdown launched in February.
In other violence Wednesday, Iraqi police say a bomb killed 11 people on bus taking them to the town of Hilla, south of Baghdad.
Police say mortar shells killed another three people in the town of Mahmudiya, also south of the capital.
Separately, the U.S. military says coalition forces detained 12 terrorist suspects during overnight raids in Baghdad and al-Anbar province.
On Tuesday, U.S. and Iraqi officials said they were trying to confirm reports that al-Qaida in Iraq leader Abu Ayyub al-Masri was killed in a clash among members of his insurgent group.