The recruits, who had just joined the force, were killed on Monday when the car bomber rammed his car into their bus near Baquba, north of Baghdad, as they travelled to the Kurdish northern region for training.
Thirteen other recruits were wounded.
At least eight more Iraqis were killed by machine-gun fire in attacks elsewhere in the country, including children in a car.
And an ambulance driver was shot through the head as he drove to a hospital in Kirkuk, security officials said.
The children, two boys aged seven and 10, died in the drive-by shooting when armed men targeted their parents' car south of Kirkuk. The parents were wounded.
Three more men were shot and killed while travelling in a car just south of Baghdad, near Iskandariya.
Two Iraqi soldiers died when their patrol was hit by a roadside bomb near Dujail, north of Baghdad.
Another soldier was killed and an officer wounded in a drive-by shooting on the road between Baiji and Tikrit.
Also on Monday, Iraqi police said armed men attacked the convoy of Unal Cevikoz, the Turkish ambassador to Iraq, in Baghdad, injuring him slightly.
The attack occurred on Baghdad's airport road, notorious for frequent assaults by fighters targeting foreigners.
And at Rustimiya, south of the capital, eight unidentified bodies were pulled out of a water purification plant. They were believed to have been in the water for more than a week.
Meanwhile, Iraqi soldiers foiled an attack on an army base north of Kirkuk.
Colonel Sarhat Qadir said the driver of the booby-trapped car, who had just dropped off a cameraman to film the attack, was shot as he approached the entrance of a military camp.
The car then blew up, killing both the driver and the cameraman who stood nearby. There were no other injuries.