Nine policemen were among the 12 people killed in two attacks on security personnel in central Iraq on Monday, police said.
A suicide bomber killed nine people, six of them police officers, when he blew up a fuel tanker in Tikrit, some 170 kilometres north of the capital Baghdad, dpa reported.
Police said 18 people were injured.
In southern Baghdad, three policemen were killed when gunmen opened fire on a police patrol.
Iraq has witnessed near-daily attacks since US troops withdrew in December 2011, raising fears of a return to the sectarian tensions that drove the country to the brink of civil war in 2006 and 2007.
The country also faces a crisis between the Shiite-led government and the country's once-dominant Sunni minority, who have been staging protests for more than three months.