In Mosul, attackers detonated a bomb near a US military patrol on Saturday, but missed the patrol and hit a school bus, killing a teenage student and wounding six others, the US military said.
The bomb exploded as the patrol was travelling through an eastern district of the city, closely followed by the minibus carrying students to a nearby high school.
"The blast hit an Iraqi school bus killing one and injuring six, all eighth graders," the military said in a statement. An agency photographer saw several badly wounded teenagers being treated at a local hospital for blast wounds.
No US soldiers were wounded in the attack but one of the assailants was killed, the statement said.
Mosul has experienced a recent surge in violence. On Friday, a car carrying Turkish security guards was attacked in the city, in Iraq's far north near the Turkish border, and four people were killed, one of them decapitated.
On Friday a car was attacked in
which four people died
Over the past six weeks, more than 150 bodies have been discovered around the city, most of them members of the Iraqi National Guard but many of them also apparently civilians.
On Saturday, two people were killed and eight wounded in a mortar attack on an election office north of Baghdad, police and hospital sources said.
They said five mortars landed on the premises in Dujail, one of many around the country providing information to potential voters ahead of the 30 January election. It will be used as a polling station on the day of the vote in six weeks' time.
Among the wounded were six Iraqi security personnel, who were guarding the office against attack in the predominantly Sunni town, about 50km north of the capital.
Also on Saturday, Iraqi police found two bodies dumped in the town of Baiji, 180km north of the capital.
One of the men had been shot in the head and the other killed by hanging, police said. Both had their arms tied behind their backs.
Key oil installations are coming
under repeated attacks in Iraq
They have not been identified and the motives for the killings, which have become increasingly common in Iraq over the course of the year, were not known.
Elsewhere, at Dakkuk, near the northern oil centre of Kirkuk, one guardsman was killed and three wounded when fighters fired on their checkpoint early on Saturday.
In other developments, Iraq's key oil infrastructure suffered five attacks in a span of 24 hours.
An oil ministry spokesman condemned the upsurge in "terrorist acts" which he said were depriving Iraqis of essential fuel and the country of desperately needed export revenues.
There were two blasts on pipelines on Saturday and three late on Friday, all of them in unstable areas around the capital or in north-central Iraq, officials said.
"These terrorist acts, which coincide with the threats from Bin Ladin, are aimed at depriving ordinary people of fuel so that the crisis worsens," the oil ministry spokesman said.
"They are costing Iraqis hundreds of millions of dollars."