Sgt Ali Abdullah Hussein says the attack was the latest by the Islamic State group as Iraqi forces close in on the last pocket of militant-held territory in the Old City neighbourhood.
The IS group's last stand in Mosul is rapidly shrinking, with the militants now controlling just over 1 square kilometre in all.
Hussein says the attack happened this morning in the area of the destroyed al-Nuri Mosque.
He said that over the past three days, at least four such attacks have targeted Iraqi forces as hundreds of civilians flee the fierce fighting in the Old City's congested streets.