Nighttime incident occurred amid tensions with the US after Iraqi protesters attacked the US Embassy in Baghdad.
General Qassem Soleimani, the head of Iran's elite Quds force, has been reported killed alongside six others following a US airstrike at Baghdad's international airport.
Iraqi officials and the state television reported that aside from Soleimani, Iraqi militia commander Abu Mahdi al-Muhandis was also killed in the attack.
Ahmed al-Assadi, a spokesman for Iraq's Popular Mobilisation Forces (PMF) umbrella grouping of Iran-backed militias, also confirmed the deaths of Soleimani and Muhandis.
Two unnamed US officials told Reuters news agency that the US carried out the targeted airstrikes.