Three of the wounded were in “grave condition” after the explosion, the Italian Defense Ministry said.
Rear Adm. Fabio Agostini said the five – three in the navy and two in the army – are part of a special forces team that was traveling back after a mission aimed at finding ISIS refugees.
Agostini told Italian Rai state TV that Iraqi armed forces members were also injured in the blast but didn’t say how many.
An Iraqi security official said the bomb exploded next to their vehicle as they were traveling just outside Kirkuk – about 165 miles north of Baghdad, wounding six Italian soldiers.
The discrepancy in the number of wounded wasn’t immediately explained.
U.S. military helicopters evacuated the soldiers to a hospital in Baghdad.
One Italian soldier lost a leg to amputation due to injuries from the bomb and another suffered serious internal injuries, Italian Gen. Nicola Lanza de Cristoforis told Rai.
Iraq declared victory against ISIS two years ago, but the group continues to stage insurgent attacks across the country.
Italy currently has more than 800 regular soldiers and some 80 special forces in Iraq.
The Associated Press contributed to this report.