A suicide bomber detonated an explosives-rigged vehicle at a checkpoint in Iraq on Sunday, killing 11 people, after which an angry crowd burned a courthouse and several homes, officials said.
The latest violence comes amid a protracted surge in nationwide bloodshed that has claimed more than 2,550 lives so far this year and sparked fears of Iraq slipping back into the all-out sectarian killings of 2006 and 2007.
The unrest has been driven principally by widespread anger among the Sunni Arab minority over claims of mistreatment at the hands of the Shiite-led government and security forces, as well as by the civil war in neighbouring Syria.
The suicide bomber attacked a police checkpoint in Dibs in northern Iraq, killing seven police and four civilians, and wounding 18 people, among them security forces members.
Following the blast, an angry crowd torched a local courthouse and five homes, including those of a police colonel and a judge.
Iraqi security forces periodically face a backlash from citizens angered by their failure to prevent attacks, but burning homes and a court is unusual.
In a village in the Sulaiman Bek area, also north of Baghdad, gunmen attacked a police officer's house, killing his father and brother and wounding two more people.
The gunmen also shot dead a Sahwa anti-Al-Qaeda militiaman nearby.
Sulaiman Bek has been repeatedly attacked by militants, who have seized part or all of the area on several occasions.
And a roadside bomb in the Dujail area, near the northern city of Tikrit, killed three people and wounded six.
Iraq's first general election since American troops left at the end of 2011 will be held on April 30, in a major test for the security forces.
While they were able to keep violence to a minimum during provincial polls last year, the security forces have failed to halt a subsequent year-long surge in unrest.
More than 320 people have been killed since the beginning of this month alone, according to AFP figures based on security and medical sources.