A suicide bomber used an ambulance to attack a police compound in central Iraq, killing up to 14 people, officials said.
Scores more were wounded in the attack in Baquba - the second targeting Iraq's security forces in two days.
On Tuesday, a suicide bomber killed about 60 people at a police recruitment centre in Tikrit, the hometown of former Iraqi leader Saddam Hussein.
Violence in Iraq has ebbed in recent years, but deadly attacks persist.
Both Baquba - 65km (40 miles) north-east of Baghdad - and Tikrit are within what is known as the Sunni Triangle, a stronghold of Iraq's insurgency.
'Bodies buried'
Most of those killed in Wednesday morning's attack were police officers, officials said.
One report said two attackers were involved. One stepped out of the ambulance and opened fire on guards at the entrance of the city's special security police centre before the vehicle was driven into the compound and detonated, reports said.
More than 60 injuries were reported, and more people are said to be buried under rubble after the explosion caused a building to collapse.
"There are more bodies buried in the ruins," a spokeswoman for Diyala's governor told Reuters news agency.
The injured included a number of children from a nearby kindergarten, said provincial spokeswoman Samira al-Shibli.
Iraqi police and army recruiting centres are often targeted by suicide bombers.
About an hour later in the nearby town of Ghalbiyah, a suicide bomber targeted a crowd of Shia pilgrims walking from Baghdad to the holy city of Karbala, killing at least two and injuring 15.
Among the wounded was the deputy head of Diyala's provincial council, Sadiq al-Husseini, and three of his bodyguards, reports said.
Anti-Shia attacks had been feared ahead of next week's commemoration of Arbain - a 40-day mourning period observed by Shia Muslims for Imam Hussein, a grandson of the Prophet Muhammad killed at the battle of Karbala in the 7th Century.
Security has been stepped up ahead of the climax of the Shia pilgrimage next week, when hundreds of thousands of pilgrims are expected to converge on Karbala.
Overall violence in Iraq has fallen sharply since the height of the sectarian killings of 2006-07, but shootings and bombings remain a daily occurrence.
US forces formally ended their combat operations last August, ahead of a planned full withdrawal later this year.
