Gunmen killed four police in an attack on Wednesday on a patrol in Taji, north of Baghdad, while two more were killed in an attack on a prison, security and medical officials said.
An interior ministry official said that unknown gunmen attacked a police patrol in Taji, killing four police, a toll confirmed by a medical official, who said the attack came at around 8:30 pm (1730 GMT).
According to the medical official, a roadside bomb exploded when police reinforcements arrived at the scene.
A police captain said that gunmen also tried to break into a prison in Taji, killing two police guards, and setting off bombs that destroyed a gate under construction and wounded five police in an observation tower.
Clashes broke out, and the area was surrounded by army and police, the captain said.
Policeman Thair Al-Muzaham, who was at the prison, said: "Two of my colleagues died in the attack, and one was wounded and is in very critical condition."
The attack comes after Al-Qaeda front group the Islamic State of Iraq said it would look to retake territory, and appealed for Sunni Arab tribes to send fighters, in a recording posted in the name of its leader Abu Bakr al-Baghdadi.
The message posted on various jihadist forums said the ISI would begin targeting judges and prosecutors, and try to help its prisoners break out of Iraqi jails.
Earlier on Wednesday, Staff Brigadier General Hamid Mohammed Qamr told AFP that Wissam Karim al-Shilal, an alleged Al-Qaeda leader accused of planning and executing an attack on an Iraqi army base on July 23 that left 15 soldiers dead, was killed in fighting with Iraqi soldiers.
Shilal was killed near Al-Adheem, north of Baghdad.
Violence in Iraq has declined from its peak in 2006-2007, but attacks remain common, killing 325 people in July according to official sources, the highest monthly toll in almost two years.