An Interior Ministry official said on Wednesday that a mortar round struck a busy central Baghdad bus station as US Defence Secretary Donald Rumsfeld was holding talks in the Iraqi capital.
Fifteen minibuses at the Alawi Hella station were slightly damaged by the mortar fire, a journalist at the scene said.
In another attack, a bomber wounded two police officers and two soldiers when he drove his booby-trapped car at a checkpoint in the southwest of the capital, the official said.
Seven Iraqi soldiers were shot and killed as they were guarding a water plant north of Baghdad.
The Defence Ministry said on Wednesday that about 20 assailants armed with hand grenades and light weapons drove up in four cars and opened fire on Tuesday on the soldiers in the town of Tarmiya, 50km north of Baghdad.
No other details were available.
In another incident, armed men kidnapped the general manager of Baghdad airport's communication along with his driver and bodyguard.
In Samarra, 95km north of Baghdad, a US military vehicle was destroyed in an explosive device in al-Amil neighbourhood north of the city, while two soldiers from Iraq rapid intervention forces were killed in an ambush in the western town of Biji.
Kuwaiti border fire
In a separate development, Iraqis protesting a metal border barrier that Kuwait is building between the two countries fired several shots across the border on Wednesday, but a security official said nobody was injured.
Iraqis try to remove a barrier put
by Kuwait inside Iraqi territory
The official, who declined to be identified, said the bullets were fired by a group of about 40 Iraqis into Kuwait.
Earlier, hundreds of Iraqis had gathered on Sunday and Monday at the border area of Umm Qasr to demand the project be stopped.
Kuwait is erecting the pipeline along the frontier which was redrawn by the United Nations after the small oil-rich state was liberated in 1991 from a seven-month Iraqi occupation.
The UN gave Kuwait 11 oil wells, some farmland and an old naval base that used to be in Iraq.
The Iraqis are protesting the barrier which they say is being built well within land owned by Iraq.