Five Iraqis, including a police officer, were killed on Tuesday in the attack that targeted a Provincial Joint Coordination Centre in this town known for its sectarian and ethnic diversity. Baquba is 60km north of Baghdad.
Nine US soldiers were wounded, while a US civilian contractor was also wounded along with six Iraqi civilians and four Iraqi police officers.
Earlier, Iraqi officials said 11 police officers were killed and 15 others wounded in an attack in Baquba, although it was not immediately clear whether the reports were describing the same incident.
Separately, the US military announced on Tuesday that two US marines and a US soldier were killed in attacks over the past three days in Iraq.
One marine was killed on Monday when his vehicle was hit by a roadside bomb during a combat operation near Fallujah, 50km west of Baghdad, once the stronghold for anti-US presence in Iraq groups.
Injured Iraqis in the emergency
room of the Baquba Hospital
One US soldier was killed on Monday in a rocket attack by fighters in the south of Baghdad, the US military said Tuesday.
A second marine was killed by a roadside bomb on Sunday during another combat operation near Fallujah in the volatile Sunni heartland, the US military said.
About 60 US military personnel have been killed in August, making it one of the deadliest months for the American military in Iraq since the 2003 invasion.
Claim of responsibility
The group of Al-Qaida's Iraq frontman Abu Musab al-Zarqawi claimed responsibility Tuesday for an attack which killed five Iraqis and two Americans in Baquba, according to an Internet statement.
One of the "lions" of a "martyrdom-seeking" brigade affiliated to the Al-Qaida Organisation in the Land of Two Rivers, "who wore an explosives belt, plunged into a group of adorers of the cross at the seat of the big crimes in Baquba," said the statement, whose authenticity could not be verified.
The statement, posted on an Islamist website, identified the bomber as "Abu al-Munzer al-Ansari al-Iraqi" but said "the enemies' losses were not known, because the operation was carried out inside the building."