A suicide attack on a police station in Baghdad's main Shia Muslim district has left 10 dead and dozens wounded.
The car was reduced to tangled wreckage
A car carrying two people sped into the compound in the Sadr City area before exploding near the main building.
Gunmen also shot dead a Spanish military attache in the city and a US soldier was killed in an ambush near Baquba, to the north-east of Baghdad.
In the Kurdish north of Iraq, gunmen attacked a police patrol, killing two officers and two civilians.
The latest violence came six months to the day since US troops took control of Baghdad, toppling the regime of Saddam Hussein.
'All I could see was fire'
Hundreds of police officers had been waiting to receive salaries in the compound when the car drove at speed through the gate at about around 0845 (0545GMT) on Thursday, despite shots fired by guards.
ATTACKS ON IRAQI POLICE
July 5: Remote-controlled bomb kills 7 police
recruits in Ramadi, 100km west of Baghdad
July 13: Bomb explodes near police station in Baghdad
suburb, killing 1
Sept 2: Car bomb hits Rasafa police HQ in eastern Baghdad, killing 1 and wounding 15
The blast killed three policemen, five civilians and two men in the car.
"I ran and got hit in the leg," said police officer Khalid Sattar Jabar, 25, from his hospital bed. "When I looked back, all I could see was fire.
Mr Jabar had caught sight of the driver of the car and described him as a man with a beard and a thick head of hair.
Iraq's police force has been the target of a series of attacks since the US-led coalition began running the country.
According to one unconfirmed report, US troops who mounted a search after Thursday's bomb attack clashed with armed members of a local Shia militia, leaving one militiaman dead and two wounded.
Shot outside home
Spanish military attache Jose Antonio Bernal Gomez was shot dead after apparently answering the door to two men at his residence in Baghdad's elite Mansour district at 0800 on Thursday.
According to the Spanish foreign ministry, the attackers had arrived in a car bearing foreign licence plates and one was dressed as a Shia cleric.
A local guard said Mr Bernal Gomez had tried to run outside when his attackers attempted to grab him and they fired at least six shots.
There are about 1,300 Spanish troops in Iraq, the majority deployed in Shia areas south of Baghdad.
Mr Bernal Gomez was Spain's second fatality in post-war Iraq. On 19 August, a Spanish naval officer seconded to the UN was one of 23 people killed in a bomb attack on the UN headquarters in Baghdad.
In Thursday's other attacks, Kurdish media report that gunmen in a car opened fire on a police vehicle in Arbil at about 0830, killing two officers as well as two civilians, one of them a woman.
Arbil's police chief blamed the attack on "a terrorist group seeking to destabilise the city".
In the attack near Baquba, in Iraq's Sunni Muslim heartland, a rocket-propelled grenade was fired at a US military convoy at about 0200, killing a soldier from the 4th Infantry Division.