Attacks targeting Iraqi police and anti-Al-Qaeda militiamen killed 15 people on Friday, in spiralling violence that has claimed almost 1,500 lives in three months and sparked fears of renewed sectarian war.
The surge in unrest has coincided with months of protests by the Sunni Arab minority and a protracted political deadlock which analysts warn could persist until general elections due next year.
The violence is the latest in a spate of attacks which have killed more than 140 people in the past week, including 27 killed on Thursday, mostly in blasts targeting cafes.
Friday's deadliest attack struck on the southern outskirts of Ramadi, capital of western Anbar province.
Two explosions went off at around midday, the first being a magnetic "sticky bomb" attached to the car of a Sahwa fighter.
As onlookers gathered at the scene, another device detonated, a common tactic used by militants in Iraq to maximise the number of casualties.
Overall, nine people were killed and 21 wounded, according to Sahwa Colonel Jubeir Nayef and Dr Ahmad al-Aani of Ramadi hospital. Most of the victims were Sahwa fighters, they said.
The Sahwa are a collection of Sunni tribal militias who turned against Al-Qaeda and joined forces with the US military from late-2006 onwards, helping to turn the tide of Iraq's bloody insurgency.
They are paid by the government, and officials have pledged to integrate them into the civil service or security forces. But they are often targeted by Al-Qaeda-linked militants who regard them as traitors.
Also on Friday, a Sahwa officer was found dead south of Baghdad after being kidnapped a day earlier, while one Sahwa fighter was killed and four others wounded in a shooting in Sharqat, north of Baghdad.
And near the town of Dujail, also north of the capital, a suicide car bomb targeting a group of policemen killed four people and wounded a dozen more, officials said.
The latest attacks pushed the overall nationwide death toll for June to 411, the third successive month the figure has topped 400, according to an AFP tally based on reports from security and medical officials. April and May saw more than 1,000 people killed in all.
Figures compiled by the United Nations, however, are higher still, pegging the death toll for April and May at more than 1,750.
Iraq has seen a rise in violence since the beginning of the year, coinciding with rallies among the Sunni Arab minority against what demonstrators see as discrimination by the Shiite-led authorities.
Analysts say a government failure to address protesters' grievances has given militant groups recruitment fodder and room to manoeuvre.