The unrest has left more than 3 900 people dead already this year, and sparked concerns Iraq is slipping back into the all-out sectarian war that plagued it in 2006 and 2007 and left tens of thousands dead.
Shootings and bombings stuck the main northern city of Mosul, as well as Baquba, Taji and Tuz Khurmatu, all north of the capital, leaving four dead and nine others wounded overall, according to security and medical officials.
In Taji, a suicide bomber tried to enter the town mayoralty offices but blew himself up at the gates to the building when police opened fire on him.
The blast killed a policeman and wounded four others.
In Mosul, meanwhile, a police major was killed when security forces approached a corpse that had been booby-trapped with explosives.
In Tuz Khurmatu and Baquba, gunmen assassinated a finance ministry official and a district chief respectively.
Violence has surged in Iraq since the beginning of the year, and is now at its highest level since 2008.
Authorities have responded with wide-ranging security operations targeting militants, but diplomats and analysts say these are not addressing the root causes of the violence.