Gunmen on Thursday attacked a checkpoint in Taji, north of Baghdad, killing the four soldiers and wounding five others, security and medical officials said.
Near Baquba, also north of the capital, a roadside bomb in a market killed four people and wounded two, while gunmen killed two police and wounded two others in another attack.
Gunmen also killed a civilian in the north Iraq city of Mosul, police and a doctor said.
And in Tikrit, another city north of Baghdad, a roadside bomb exploded near a police patrol, wounding two policemen.
Thursday's attacks come a day after 22 people were killed in violence, among them were 12 shot dead in Baghdad and eight militants killed by security forces.
Violence in Iraq is down from its peak in 2006 and 2007, but attacks remain common. More than 200 people have been killed in each of the first five months of this year.