The militia fighters were killed when Islamic State militants commandeered an armored Humvee, rigged it with explosives and drove it into a school where the fighters were based near Dijla district, 20 km (15 miles) south of the city of Samarra.
They followed up with mortar and machine gun fire, a source at the Samarra Operations Command said, and clashes continued.
Radical Sunni Islamic State fighters, who control much of north and west Iraq, are battling the army, Kurdish peshmerga forces and Shi’ite militias allied to the Shi’ite-led government in Baghdad, which is also supported by U.S.-led air power.
Islamic State have lost some ground since they swept through northern Iraq toward Baghdad in June, but they continue to hold swathes of territory and carry out attacks on many fronts.
A local commander said several militants were killed in Iraqi air strikes on Wednesday against an Islamic State target near the town of Muqdadiya, north of Baghdad.
Around the capital, bombs killed six people and wounded 23 others, police and medical sources said. A soldier was killed by a roadside bomb in Tarmiya, north of Baghdad while two civilians were killed in an explosion in the agricultural area of Arab-Jubour to the south.
A third bomb, on a commercial street in Mada’in, also to the south of Baghdad, killed three civilians.
In the western, Sunni Muslim province of Anbar, Islamic State attacked an army post in the town of Garma.
Three people were killed in the fighting and the militants, who have targeted economic and agricultural facilities as well as military positions across the country, took control of a flour factory and potato storage facility. -Reuters